Remove redundant fixture mongo

tests/app/test_optimade.py

tests/app/test_resources.py

tests/app/v1/routers/test_datasets.py

tests/app/v1/routers/test_entries_edit.py

tests/app/v1/routers/test_uploads.py

tests/archive/test_archive.py

tests/conftest.py

tests/data/test_examples.py

tests/datamodel/metainfo/eln/test_labfolder.py

tests/datamodel/metainfo/eln/test_openbis.py

tests/datamodel/metainfo/eln/test_perovskite_database.py

tests/datamodel/metainfo/eln/test_system.py

tests/examples/test_archive_query.py

tests/metainfo/test_mongodb_extension.py

tests/parsing/test_tabular.py

...erovskite_solar_cell_database/test_perovskite_database.py

tests/processing/test_base.py

tests/processing/test_data.py

tests/test_cli.py

tests/test_doi.py