Fix AzureKeyVaultSettingsSource problem in case of field with undersc…

…ore (pydantic#415)

pydantic_settings/sources.py

@@ -2034,7 +2034,7 @@ def __getitem__(self, key: str) -> str | None:
         if key not in self._loaded_secrets:
             try:
                 self._loaded_secrets[key] = self._secret_client.get_secret(key).value
-            except ResourceNotFoundError:  # type: ignore
+            except Exception:
                 raise KeyError(key)
 
         return self._loaded_secrets[key]