Use Java version wildcard in image building docs

Fixes gh-22916

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/packaging-oci-image.adoc

@@ -115,7 +115,8 @@ $ gradle bootBuildImage --builder=mine/java-cnb-builder --runImage=mine/java-cnb
 ==== Builder Configuration
 If the builder exposes configuration options, those can be set using the `environment` property.
 
-The following example assumes that the default builder defines a `BP_JVM_VERSION` property (typically used to customize the JDK version the image should use):
+The following example assumes that the default builder recognizes a `BP_JVM_VERSION` property.
+This property is typically used to customize the JDK version the image should use by specifying the major version and a wildcard for the rest of the version:
 
 [source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
 .Groovy

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

@@ -9,7 +9,7 @@ bootJar {
 
 // tag::env[]
 bootBuildImage {
-	environment = ["BP_JVM_VERSION" : "13.0.1"]
+	environment = ["BP_JVM_VERSION" : "8.*"]
 }
 // end::env[]
 

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

@@ -7,7 +7,7 @@ plugins {
 
 // tag::env[]
 tasks.getByName<BootBuildImage>("bootBuildImage") {
-	environment = mapOf("BP_JVM_VERSION" to "13.0.1")
+	environment = mapOf("BP_JVM_VERSION" to "8.*")
 }
 // end::env[]
 

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/docs/asciidoc/packaging-oci-image.adoc

@@ -152,7 +152,8 @@ The builder and run image can be specified on the command line as well, as shown
 ==== Builder Configuration
 If the builder exposes configuration options using environment variables, those can be set using the `env` attributes.
 
-The following example assumes that the default builder defines a `BP_JVM_VERSION` property (typically used to customize the JDK version the image should use):
+The following example assumes that the default builder recognizes a `BP_JVM_VERSION` property.
+This property is typically used to customize the JDK version the image should use by specifying the major version and a wildcard for the rest of the version:
 
 [source,xml,indent=0,subs="verbatim,attributes"]
 ----
@@ -166,7 +167,7 @@ The following example assumes that the default builder defines a `BP_JVM_VERSION
 					<configuration>
 						<image>
 							<env>
-								<BP_JVM_VERSION>13.0.1</BP_JVM_VERSION>
+								<BP_JVM_VERSION>8.*</BP_JVM_VERSION>
 							</env>
 						</image>
 					</configuration>