fix(utils.py): correctly re-raise the headers from an exception, if present

Fixes issue where retry after on router was not using azure / openai numbers

.pre-commit-config.yaml

@@ -1,12 +1,12 @@
 repos:
 -   repo: local
     hooks:
-    -   id: mypy
-        name: mypy
-        entry: python3 -m mypy --ignore-missing-imports
-        language: system
-        types: [python]
-        files: ^litellm/
+    # -   id: mypy
+    #     name: mypy
+    #     entry: python3 -m mypy --ignore-missing-imports
+    #     language: system
+    #     types: [python]
+    #     files: ^litellm/
     -   id: isort
         name: isort
         entry: isort