Adjust -j values for gcc-openmpi AT2 job

Adjust the -j values for gcc-openmpi AT2 from 32 to 16 as we add more
and more AT2 jobs to give the machine more space for other jobs.

Story ref: TRILFRAME-629

Author: achauphan

.github/workflows/AT2.yml

@@ -70,7 +70,7 @@ jobs:
           bash -l -c "cmake -C PR-configuration.cmake -C package-enables.cmake ${GITHUB_WORKSPACE}"
       - name: build trilinos
         working-directory: /home/Trilinos/build
-        run: bash -l -c "ninja -j36"
+        run: bash -l -c "ninja -j16"
       - name: ctest
         working-directory: /home/Trilinos/build
-        run: bash -l -c "ctest -j36"
+        run: bash -l -c "ctest -j16"