Update testcluster tag in .gitlab-ci.yml

.gitlab-ci.yml

@@ -60,7 +60,7 @@ gcc_9_mpionly:
       WALBERLA_BUILD_WITH_METIS: "OFF"
       WALBERLA_BUILD_WITH_PARMETIS: "OFF"
    tags:
-      - testfront
+      - testcluster
    artifacts:
       paths:
          - build
@@ -87,4 +87,4 @@ test:
       - cd $CI_PROJECT_DIR/build/tests/core
       - ctest -C $CMAKE_BUILD_TYPE --output-on-failure -j $NUM_CORES -T Test -R ReduceTest
    tags:
-      - testfront
+      - testcluster