Migrate from adopt

https://github.com/actions/setup-java#supported-distributions
https://blog.adoptopenjdk.net/2021/08/goodbye-adoptopenjdk-hello-adoptium/

PiperOrigin-RevId: 394558213

Author: cushon

.github/workflows/ci.yml

@@ -63,7 +63,7 @@ jobs:
         uses: actions/setup-java@v2
         with:
           java-version: ${{ matrix.java }}
-          distribution: 'adopt'
+          distribution: 'zulu'
       - name: 'Install'
         shell: bash
         run: mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
@@ -90,7 +90,7 @@ jobs:
         uses: actions/setup-java@v2
         with:
           java-version: 15
-          distribution: 'adopt'
+          distribution: 'zulu'
           server-id: sonatype-nexus-snapshots
           server-username: CI_DEPLOY_USERNAME
           server-password: CI_DEPLOY_PASSWORD