Drop flaky marker from the fetchlimit system test

With the per-domain limit and clients-per-query spill checks no longer
sensitive to fetch-counter timing, the test no longer needs the
flaky-retry workaround.

Assisted-by: Claude:claude-opus-4-7

bin/tests/system/fetchlimit/tests_sh_fetchlimit.py

@@ -23,6 +23,5 @@ pytestmark = pytest.mark.extra_artifacts(
 )
 
 
-@pytest.mark.flaky(max_runs=3)
 def test_fetchlimit(run_tests_sh):
     run_tests_sh()