Stop caching ~/.m2 across Gradle-based CI tasks

See gh-19931

Author: wilkinsona

ci/tasks/build-pr-project.yml

@@ -5,7 +5,6 @@ inputs:
 outputs:
 - name: distribution-repository
 caches:
-- path: maven
 - path: gradle
 params:
   CI: true

ci/tasks/build-project.yml

@@ -5,7 +5,6 @@ inputs:
 outputs:
 - name: distribution-repository
 caches:
-- path: maven
 - path: gradle
 - path: embedmongo
 params:

ci/tasks/stage.yml

@@ -12,7 +12,6 @@ params:
   GRADLE_ENTERPRISE_CACHE_PASSWORD:
   GRADLE_ENTERPRISE_URL: https://ge.spring.io
 caches:
-- path: maven
 - path: gradle
 run:
   path: git-repo/ci/scripts/stage.sh