[FLINK-37225] Remove remaining test resources of Gelly

[X-czh]

What is the purpose of the change

Remove remaining test resources of Gelly, which is removed from the codebase in FLINK-29668.

Brief change log

Remove remaining test resources of Gelly.

[flinkbot]

CI report:

• c42c4ee Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[davidradl]

I was looking to see when we decided that Gelly is no longer supported so should not be tested; I could not see anything in the Jira as to the history behind this.

[X-czh]

@davidradl I'm not familiar with the background either, it was removed in Flink 1.16. @MartijnVisser Maybe you can provide more background here

[MartijnVisser]

I was looking to see when we decided that Gelly is no longer supported so should not be tested; I could not see anything in the Jira as to the history behind this.

Decisions like this one to delete something, in this case Gelly, per https://flink.apache.org/how-to-contribute/contribute-code/#consensus should be discussed on the Dev mailing list.

See https://lists.apache.org/thread/kfwq87t5b79ndknndhodz6o8b0d8y41v for the discussion thread and https://lists.apache.org/thread/ng5t85t1lnmzrld4vvlk0mglq3fcgj50 for the result of the vote thread

[X-czh]

@MartijnVisser Hi, if there's no other issues, would you mind helping to merge this?