Replace discouraged pkg_resources for Python 3.9+

See https://setuptools.readthedocs.io/en/latest/pkg_resources.html

gajim/common/configpaths.py

@@ -118,8 +118,12 @@ def __init__(self) -> None:
             self.cache_root = Path(GLib.get_user_cache_dir()) / 'gajim'
             self.data_root = Path(GLib.get_user_data_dir()) / 'gajim'
 
+        if sys.version_info < (3, 9):
             import pkg_resources
             basedir = Path(pkg_resources.resource_filename("gajim", "."))
+        else:
+            import importlib.resources
+            basedir = importlib.resources.files('gajim')
 
         source_paths = [
             ('DATA', basedir / 'data'),

setup.cfg

@@ -24,7 +24,7 @@ install_requires =
     keyring
     nbxmpp>=2.0.1
     packaging
-    setuptools
+    setuptools; python_version < '3.9'
     precis-i18n>=1.0.0
     pyOpenSSL>=16.2
     pycairo>=1.16.0