Encourage use of maven-publish plugin in Gradle docs

See gh-25299

Author: robert-smith-911

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/publishing.adoc

@@ -3,45 +3,45 @@
 
 
 
-[[publishing-your-application-maven]]
-=== Publishing with the Maven Plugin
-When the {maven-plugin}[`maven` plugin] is applied, an `Upload` task for the `bootArchives` configuration named `uploadBootArchives` is automatically created.
-By default, the `bootArchives` configuration contains the archive produced by the `bootJar` or `bootWar` task.
-The `uploadBootArchives` task can be configured to publish the archive to a Maven repository:
+[[publishing-your-application-maven-publish]]
+=== Publishing with the Maven-publish Plugin
+To publish your Spring Boot jar or war, add it to the publication using the `artifact` method on `MavenPublication`.
+Pass the task that produces that artifact that you wish to publish to the `artifact` method.
+For example, to publish the artifact produced by the default `bootJar` task:
 
 [source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
 .Groovy
 ----
-include::../gradle/publishing/maven.gradle[tags=upload]
+include::../gradle/publishing/maven-publish.gradle[tags=publishing]
 ----
 
 [source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
 .Kotlin
 ----
-include::../gradle/publishing/maven.gradle.kts[tags=upload]
+include::../gradle/publishing/maven-publish.gradle.kts[tags=publishing]
 ----
 
 
 
-[[publishing-your-application-maven-publish]]
-=== Publishing with the Maven-publish Plugin
-To publish your Spring Boot jar or war, add it to the publication using the `artifact` method on `MavenPublication`.
-Pass the task that produces that artifact that you wish to publish to the `artifact` method.
-For example, to publish the artifact produced by the default `bootJar` task:
+[[publishing-your-application-maven]]
+=== Publishing with the Maven Plugin
+When the {maven-plugin}[`maven` plugin] is applied, an `Upload` task for the `bootArchives` configuration named `uploadBootArchives` is automatically created.
+By default, the `bootArchives` configuration contains the archive produced by the `bootJar` or `bootWar` task.
+The `uploadBootArchives` task can be configured to publish the archive to a Maven repository:
 
 [source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
 .Groovy
 ----
-include::../gradle/publishing/maven-publish.gradle[tags=publishing]
+include::../gradle/publishing/maven.gradle[tags=upload]
 ----
 
 [source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
 .Kotlin
 ----
-include::../gradle/publishing/maven-publish.gradle.kts[tags=publishing]
+include::../gradle/publishing/maven.gradle.kts[tags=upload]
 ----
 
-
+WARNING: The maven plugin has been deprecated in Gradle 6.0 and is scheduled to be removed in Gradle 7.0. Please use the maven-publish plugin instead.
 
 [[publishing-your-application-distribution]]
 === Distributing with the Application Plugin