resourceutil: use `from importlib import resources`
Without this patch, we get the following error from when trying to run
hg with PyOxidizer:
module 'importlib' has no attribute 'resources'
I don't know what why that happens, but `from importlib import
resources` is the form I would prefer anyway, so let's use that now
that the impoort-checker has been fixed.
Differential Revision: https://phab.mercurial-scm.org/D7701