Add typing to test_groupby.py (#8890)

* Update test_groupby.py

* Update pyproject.toml

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* Update test_groupby.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update test_groupby.py

* Update test_groupby.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update test_groupby.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: Illviljan

pyproject.toml

@@ -171,7 +171,6 @@ module = [
   "xarray.tests.test_dask",
   "xarray.tests.test_dataarray",
   "xarray.tests.test_duck_array_ops",
-  "xarray.tests.test_groupby",
   "xarray.tests.test_indexing",
   "xarray.tests.test_merge",
   "xarray.tests.test_missing",