Remove plugin management for Maven's site plugin

Closes gh-19085

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -233,7 +233,6 @@
 		<maven-javadoc-plugin.version>3.1.1</maven-javadoc-plugin.version>
 		<maven-resources-plugin.version>3.1.0</maven-resources-plugin.version>
 		<maven-shade-plugin.version>3.2.1</maven-shade-plugin.version>
-		<maven-site-plugin.version>3.8.2</maven-site-plugin.version>
 		<maven-source-plugin.version>3.2.0</maven-source-plugin.version>
 		<maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
 		<maven-war-plugin.version>3.2.3</maven-war-plugin.version>
@@ -3323,11 +3322,6 @@
 					<artifactId>maven-shade-plugin</artifactId>
 					<version>${maven-shade-plugin.version}</version>
 				</plugin>
-				<plugin>
-					<groupId>org.apache.maven.plugins</groupId>
-					<artifactId>maven-site-plugin</artifactId>
-					<version>${maven-site-plugin.version}</version>
-				</plugin>
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-source-plugin</artifactId>

spring-boot-project/spring-boot-parent/pom.xml

@@ -318,10 +318,6 @@
 					<artifactId>maven-plugin-plugin</artifactId>
 					<version>3.6.0</version>
 				</plugin>
-				<plugin>
-					<groupId>org.apache.maven.plugins</groupId>
-					<artifactId>maven-site-plugin</artifactId>
-				</plugin>
 				<plugin>
 					<groupId>org.basepom.maven</groupId>
 					<artifactId>duplicate-finder-maven-plugin</artifactId>