Remove dependency on https://repo.spring.io/plugins-release

It turns out the repository is required for a plugin that the project
does not use. This commit removes the declaration and adapt CI
accordingly.

Closes gh-1813

.github/workflows/build-and-deploy-snapshot.yml

@@ -19,8 +19,6 @@ jobs:
         uses: ./.github/actions/build
         with:
           develocity-access-key: ${{ secrets.DEVELOCITY_ACCESS_KEY }}
-          opensource-repository-password: ${{ secrets.ARTIFACTORY_PASSWORD }}
-          opensource-repository-username: ${{ secrets.ARTIFACTORY_USERNAME }}
           publish: true
       - name: Deploy
         uses: spring-io/artifactory-deploy-action@26bbe925a75f4f863e1e529e85be2d0093cac116 # v0.0.1

.github/workflows/build-pull-request.yml

@@ -22,8 +22,6 @@ jobs:
         env:
           CI: 'true'
           GRADLE_ENTERPRISE_URL: 'https://ge.spring.io'
-          SPRING_REPOSITORY_PASSWORD: ${{ secrets.ARTIFACTORY_PASSWORD }}
-          SPRING_REPOSITORY_USERNAME: ${{ secrets.ARTIFACTORY_USERNAME }}
         run: ./gradlew -Dorg.gradle.internal.launcher.welcomeMessageEnabled=false --no-daemon --no-parallel --continue build
       - name: Print JVM Thread Dumps When Cancelled
         if: cancelled()