Update Gradle test scripts to avoid warnings with 8.12

Closes gh-43496

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/getting-started/apply-plugin-snapshot.gradle

@@ -1,6 +1,8 @@
 buildscript {
 	repositories {
-		maven { url 'https://repo.spring.io/libs-snapshot' }
+		maven {
+			url = 'https://repo.spring.io/libs-snapshot'
+		}
 	}
 
 	dependencies {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/getting-started/milestone-settings.gradle

@@ -1,6 +1,8 @@
 pluginManagement {
 	repositories {
-		maven { url 'https://repo.spring.io/milestone' }
+		maven {
+			url = 'https://repo.spring.io/milestone'
+		}
 		gradlePluginPortal()
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/getting-started/snapshot-settings.gradle

@@ -1,7 +1,11 @@
 pluginManagement {
 	repositories {
-		maven { url 'https://repo.spring.io/milestone' }
-		maven { url 'https://repo.spring.io/snapshot' }
+		maven {
+			url = 'https://repo.spring.io/milestone'
+		}
+		maven {
+			url = 'https://repo.spring.io/snapshot'
+		}
 		gradlePluginPortal()
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/getting-started/typical-plugins.gradle.kts

@@ -8,8 +8,9 @@ apply(plugin = "io.spring.dependency-management")
 // end::apply[]
 
 tasks.register("verify") {
+	val plugins = project.plugins
 	doLast {
-		project.plugins.getPlugin(JavaPlugin::class)
-		project.plugins.getPlugin(io.spring.gradle.dependencymanagement.DependencyManagementPlugin::class)
+		plugins.getPlugin(JavaPlugin::class)
+		plugins.getPlugin(io.spring.gradle.dependencymanagement.DependencyManagementPlugin::class)
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/configure-bom.gradle

@@ -24,5 +24,7 @@ dependencyManagement {
 }
 
 repositories {
-	maven { url 'repository' }
+	maven {
+		url = 'repository'
+	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/configure-platform.gradle

@@ -14,7 +14,9 @@ dependencies {
 }
 
 repositories {
-	maven { url 'repository' }
+	maven {
+		url = 'repository'
+	}
 }
 
 configurations.all {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/custom-version-with-platform.gradle

@@ -9,7 +9,9 @@ dependencies {
 }
 
 repositories {
-	maven { url 'repository' }
+	maven {
+		url = 'repository'
+	}
 }
 
 configurations.all {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/custom-version.gradle

@@ -19,7 +19,9 @@ ext['slf4j.version'] = '1.7.20'
 // end::custom-version[]
 
 repositories {
-	maven { url 'repository' }
+	maven {
+		url = 'repository'
+	}
 }
 
 task slf4jVersion {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/custom-version.gradle.kts

@@ -27,7 +27,8 @@ the<DependencyManagementExtension>().apply {
 }
 
 tasks.register("slf4jVersion") {
+	val dependencyManagement = project.the<DependencyManagementExtension>()
 	doLast {
-		println(project.the<DependencyManagementExtension>().managedVersions["org.slf4j:slf4j-api"])
+		println(dependencyManagement.managedVersions["org.slf4j:slf4j-api"])
 	}
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/depend-on-plugin-milestone.gradle

@@ -1,6 +1,8 @@
 buildscript {
 	repositories {
-		maven { url 'https://repo.spring.io/libs-milestone' }
+		maven {
+			url = 'https://repo.spring.io/libs-milestone'
+		}
 	}
 
 	dependencies {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/managing-dependencies/depend-on-plugin-snapshot.gradle

@@ -1,6 +1,8 @@
 buildscript {
 	repositories {
-		maven { url 'https://repo.spring.io/libs-snapshot' }
+		maven {
+			url = 'https://repo.spring.io/libs-snapshot'
+		}
 	}
 
 	dependencies {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/antora/modules/gradle-plugin/examples/publishing/maven-publish.gradle

@@ -13,7 +13,7 @@ publishing {
 	}
 	repositories {
 		maven {
-			url 'https://repo.example.com'
+			url = 'https://repo.example.com'
 		}
 	}
 }