TST verify return none inplace in tests/indexing
verify we return none for all inplace calls in tests/indexing

related: https://github.com/pandas-dev/pandas/pull/35210

**build failed**, it says

ci/run_tests.sh

ImportError while loading conftest '/home/travis/build/pandas-dev/pandas/pandas/conftest.py'.

ImportError: C extension: 'dtypes' from partially initialized module 'pandas._libs.tslibs' (most likely due to a circular import) (/home/travis/build/pandas-dev/pandas/pandas/_libs/tslibs/__init__.py) not built. If you want to import pandas from the source directory, you may need to run 'python setup.py build_ext --inplace --force' to build the C extensions first.

The command "ci/run_tests.sh" exited with 4. had a similar issue locally and had to recompile everything ... @r-toroxel Thanks for the PR. The branch has conflicts with master. can you merge upstream/master thanks @r-toroxel 