build: remove pkg_resources in docs/conf.py (#1410)

Co-authored-by: arithmetic1728 <58957152+arithmetic1728@users.noreply.github.com>

Author: parthea

docs/conf.py

@@ -13,7 +13,7 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import pkg_resources
+import google.auth
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -66,7 +66,7 @@
 # built documents.
 #
 # The short X.Y version.
-version = pkg_resources.get_distribution("google-auth").version
+version = google.auth.__version__
 # The full version, including alpha/beta/rc tags.
 release = version