fix: make the comma check more specific through a regex

Author: MarcoP9

packages/http/httpx/kiota_http/middleware/retry_handler.py

@@ -1,5 +1,6 @@
 import datetime
 import random
+import re
 import time
 from email.utils import parsedate_to_datetime
 
@@ -202,7 +203,9 @@ def _parse_retry_after(self, retry_after):
         Helper to parse Retry-After and get value in seconds.
         """
         try:
-            retry_after = retry_after.split(",")[0] if "," in retry_after else retry_after
+            retry_after = retry_after.split(",")[0] if re.match(
+                r"(\d{2}),\d{3}$", retry_after
+            ) else retry_after
             delay = int(retry_after)
         except ValueError:
             # Not an integer? Try HTTP date