Backport PR #42237: TST/CI: Reduce number of unnecessary numba tests in groupby ops (#42241)

Co-authored-by: Matthew Roeschke <[email protected]>

Author: meeseeksmachine

pandas/tests/groupby/conftest.py

@@ -137,13 +137,17 @@ def parallel(request):
     return request.param
 
 
-@pytest.fixture(params=[True, False])
+# Can parameterize nogil & nopython over True | False, but limiting per
+# https://github.com/pandas-dev/pandas/pull/41971#issuecomment-860607472
+
+
+@pytest.fixture(params=[False])
 def nogil(request):
     """nogil keyword argument for numba.jit"""
     return request.param
 
 
-@pytest.fixture(params=[True, False])
+@pytest.fixture(params=[True])
 def nopython(request):
     """nopython keyword argument for numba.jit"""
     return request.param