Revert "Note the CI dulwich install in the Git backend test docstring"

This reverts commit 5959f915fa46328dcf8fbb95bae676e862a29a83.

That commit existed only to touch a .py file so CI's path filter would run
the test suite against the dulwich install in the preceding commit. The
docstring change itself is not worth keeping.

netbox/core/tests/test_data_backends.py

@@ -62,8 +62,7 @@ class GitBackendCredentialIntegrationTestCase(TestCase):
     Integration tests that verify GitBackend correctly applies credential logic.
 
     These tests require dulwich to be installed and verify the full integration
-    of the credential handling in GitBackend.fetch(). dulwich is the optional
-    'git' extra, so CI installs it explicitly; see .github/workflows/ci.yml.
+    of the credential handling in GitBackend.fetch().
     """
 
     def _get_clone_kwargs(self, url, **params):