Use raw string in TestTargetFileSearch docstirng

Using a raw string allows the use of backslashes
in the docstring comment whithout them being interpreted
as an escape character.

It also silences pylint W1401: anomalous-backslash-in-string.

Signed-off-by: Teodora Sechkova <[email protected]>

Author: sechkova

tests/test_updater_delegation_graphs.py

@@ -323,7 +323,7 @@ def test_invalid_metadata(self, test_data: DelegationsTestCase) -> None:
 
 
 class TestTargetFileSearch(TestDelegations):
-    """
+    r"""
     Create a single repository with the following delegations:
 
       targets