Adjust redirect URL for file deletion in a SAC (#4420)

* Update views.py

Addresses any potentially invalid redirect URL (from user input) with django's factory routine for validating URLs.

* Linting

backend/report_submission/views.py

@@ -608,7 +608,9 @@ def post(self, request, *args, **kwargs):
             )
 
             logger.info("The file has been successfully deleted.")
-            return redirect(f"/audit/submission-progress/{report_id}")
+            return Util.validate_redirect_url(
+                f"/audit/submission-progress/{sac.report_id}"
+            )
 
         except SingleAuditChecklist.DoesNotExist:
             logger.error(f"Audit: {report_id} not found")