Revert "Update Gradle and AGP to v8.0 (#283)" (#295)

This reverts commit cda0606a0d.

.github/workflows/nightly.yml

@@ -16,11 +16,6 @@ jobs:
     if: ${{ github.repository == 'vector-im/element-x-android' }}
     steps:
       - uses: actions/checkout@v3
-      - name: Use JDK 17
-        uses: actions/setup-java@v3
-        with:
-          distribution: 'temurin' # See 'Supported distributions' for available options
-          java-version: '17'
       - name: Install towncrier
         run: |
           python3 -m pip install towncrier