Remove deprecated pkg_resources about silx

[t20100]

pkg_resources is only used with Python3.8:

silx/src/silx/resources/__init__.py

Lines 72 to 73 in 0abd43e

	if sys.version_info < (3, 9):
	import pkg_resources

For newer versions of Python, importlib.resources.files and importlib.resources.as_file are used instead.

Complete removal of pkg_resources will be done when dropping Python3.8.

[woutdenolf]

We could use importlib_resources for python <3.9 like https://github.com/silx-kit/pyFAI/pull/2087/files. But you can close the issue if you think it is not worth it.

[t20100]

Python3.8 end of life is in about 6 months, at the same time it shouldn't be a big deal to use the backport lib.