GH-90699: fix refleak in _testcapimodule.c

[kumaraditya303]

• Issue: Replace _Py_IDENTIFIER() with statically initialized objects. #90699

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @kumaraditya303 for commit 5435423 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[corona10]

I check the leak and solution through

./python.exe -m test test_finalization -R 3:3
Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 3.73 Run tests sequentially
0:00:00 load avg: 3.73 [1/1] test_finalization
beginning 6 repetitions
123456
......

== Tests result: SUCCESS ==

1 test OK.

Total duration: 1.0 sec
Tests result: SUCCESS

But please take a look at #99236 (comment) nit message.

[corona10]

lgtm!