Fix Cython language_level not set

[kounelisagis]

When running both pipx run build or python -m build, I get:

<string>:9: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html

I followed this migration guide: https://importlib-resources.readthedocs.io/en/latest/migration.html#pkg-resources-resource-filename

Also fixed: FutureWarning: Cython directive 'language_level' not set, using '3str' for now (Py3). This has changed from earlier releases! File: /Users/agis/TileDB_workspace/TileDB-Py/tiledb/libtiledb.pxd