Remove Dataflow Portability test suite from mass_comment.py

This test suite seems to be disabled: https://ci-beam.apache.org/job/beam_PostCommit_Java11_Examples_Dataflow_Portability/

I suspect what we want to test here is the same as "Run Java 11 Examples on Dataflow Runner V2" which is running fine: https://ci-beam.apache.org/job/beam_PostCommit_Java_Examples_Dataflow_V2_java11/

release/src/main/scripts/mass_comment.py

@@ -61,7 +61,6 @@ COMMENTS_TO_ADD = [
     "Run Java Examples_Flink",
     "Run Java Examples_Spark",
     "Run Java Flink PortableValidatesRunner Streaming",
-    "Run Java Portability examples on Dataflow with Java 11",
     "Run Java PostCommit",
     "Run Java PreCommit",
     "Run Java Samza PortableValidatesRunner",