Fix property name in gradle plugin documentation

See gh-25454

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-build-image-publish.gradle

@@ -21,3 +21,9 @@ bootBuildImage {
 	}
 }
 // end::publish[]
+
+task bootBuildImagePublish {
+    doFirst {
+        println(tasks.bootBuildImage.publish)
+    }
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-build-image-publish.gradle.kts

@@ -13,7 +13,7 @@ tasks.getByName<BootJar>("bootJar") {
 // tag::publish[]
 tasks.getByName<BootBuildImage>("bootBuildImage") {
 	imageName = "docker.example.com/library/${project.name}"
-	publish = true
+	isPublish = true
 	docker {
 		publishRegistry {
 			username = "user"
@@ -24,3 +24,9 @@ tasks.getByName<BootBuildImage>("bootBuildImage") {
 	}
 }
 // end::publish[]
+
+tasks.register("bootBuildImagePublish") {
+    doFirst {
+        println(tasks.getByName<BootBuildImage>("bootBuildImage").isPublish)
+    }
+}