Upgrade to the latest Framework 6.0.x release

Closes gh-40929

gradle.properties

@@ -14,6 +14,7 @@ kotlinVersion=1.9.24
 mavenVersion=3.9.4
 nativeBuildToolsVersion=0.9.28
 springFrameworkVersion=6.1.8
+springFramework60xVersion=6.0.21
 tomcatVersion=10.1.24
 
 kotlin.stdlib.default.dependency=false

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/build.gradle

@@ -17,7 +17,7 @@ configurations.all {
 			// Downgrade Spring Framework as Gradle cannot cope with 6.1.0-M1's
 			// multi-version jar files with bytecode in META-INF/versions/21
 			if (dependency.requested.group.equals("org.springframework")) {
-				dependency.useVersion("6.0.10")
+				dependency.useVersion("$springFramework60xVersion")
 			}
 			// We manage the version of commons-compress here rather than
 			// in spring-boot-parent to minimize conflicts with Testcontainers

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/build.gradle

@@ -53,7 +53,7 @@ configurations {
 				// Downgrade Spring Framework as Gradle cannot cope with 6.1.0-M1's
 				// multi-version jar files with bytecode in META-INF/versions/21
 				if (dependency.requested.group.equals("org.springframework")) {
-					dependency.useVersion("6.0.10")
+					dependency.useVersion("$springFramework60xVersion")
 				}
 				// We manage the version of commons-compress here rather than
 				// in spring-boot-parent to minimize conflicts with Testcontainers

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/build.gradle

@@ -27,7 +27,7 @@ configurations {
 				// Downgrade Spring Framework as Gradle cannot cope with 6.1.0-M1's
 				// multi-version jar files with bytecode in META-INF/versions/21
 				if (dependency.requested.group.equals("org.springframework")) {
-					dependency.useVersion("6.0.10")
+					dependency.useVersion("$springFramework60xVersion")
 				}
 				// We manage the version of commons-compress here rather than
 				// in spring-boot-parent to minimize conflicts with Testcontainers

spring-boot-system-tests/spring-boot-image-tests/build.gradle

@@ -22,7 +22,7 @@ configurations {
 				// Downgrade Spring Framework as Gradle cannot cope with 6.1.0-M1's
 				// multi-version jar files with bytecode in META-INF/versions/21
 				if (dependency.requested.group.equals("org.springframework")) {
-					dependency.useVersion("6.0.10")
+					dependency.useVersion("$springFramework60xVersion")
 				}
 			}
 		}