Fix duplicate Date headers in Flask WSGI responses (#64726)

Author: abhijeets25012-tech

providers/fab/src/airflow/providers/fab/www/app.py

@@ -59,6 +59,14 @@ def create_app(enable_plugins: bool):
     from airflow.providers.fab.auth_manager.fab_auth_manager import FabAuthManager
 
     flask_app = Flask(__name__)
+
+    @flask_app.after_request
+    def remove_duplicate_date_header(response):
+        # Remove the application-level Date header so the ASGI/WSGI server
+        # can emit a single Date header for the final response.
+        response.headers.pop("Date", None)
+        return response
+
     flask_app.secret_key = conf.get("api", "SECRET_KEY")
     flask_app.config["SQLALCHEMY_DATABASE_URI"] = conf.get("database", "SQL_ALCHEMY_CONN")
     flask_app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False