fix: Remove keyword only argument for RequestsMiddleware

Remove keyword only arguments from request middleware. This causes
django to fail when attempting to load middleware. Django currently only
supports handlers being passed in as args.

google/cloud/logging_v2/handlers/middleware/request.py

@@ -42,7 +42,7 @@ def _get_django_request():
 class RequestMiddleware(MiddlewareMixin):
     """Saves the request in thread local"""
 
-    def __init__(self, *, get_response=None):
+    def __init__(self, get_response=None):
         self.get_response = get_response
 
     def process_request(self, request):