cancel old CI (#3649)

.yamato/com.unity.ml-agents-pack.yml

     packages:
       paths:
         - "upm-ci~/packages/**/*"
+  triggers:
+    cancel_old_ci: true

.yamato/com.unity.ml-agents-test.yml

   dependencies:
     - .yamato/com.unity.ml-agents-pack.yml#pack
   triggers:
+    cancel_old_ci: true
     changes:
       only:
         - "com.unity.ml-agents/**"

.yamato/protobuf-generation-test.yml

       echo "Apply the patch with the command 'git apply proto.patch'";                                  \
       git diff -- :/ ":(exclude,top)$CS_PROTO_PATH/*.meta" > artifacts/proto.patch; exit $GIT_ERR; }
   triggers:
+    cancel_old_ci: true
     changes:
       only:
         - "protobuf-definitions/**"

.yamato/standalone-build-test.yml

     - pip install pyyaml
     - python -u -m ml-agents.tests.yamato.standalone_build_tests
   triggers:
+    cancel_old_ci: true
     changes:
       only:
         - "com.unity.ml-agents/**"

.yamato/training-int-tests.yml

     - pip install pyyaml
     - python -u -m ml-agents.tests.yamato.training_int_tests
   triggers:
+    cancel_old_ci: true
     changes:
       only:
         - "com.unity.ml-agents/**"