fix string_to_dict test (#7571)

Author: lhoestq

src/datasets/utils/py_utils.py

@@ -180,7 +180,6 @@ def string_to_dict(string: str, pattern: str) -> Optional[dict[str, str]]:
         Optional[dict[str, str]]: dictionary of variable -> value, retrieved from the input using the pattern, or
         `None` if the string does not match the pattern.
     """
-    pattern = pattern.encode("unicode_escape").decode("utf-8")  # C:\\Users -> C:\\\\Users for Windows paths
     pattern = re.sub(r"{([^:}]+)(?::[^}]+)?}", r"{\1}", pattern)  # remove format specifiers, e.g. {rank:05d} -> {rank}
     regex = re.sub(r"{(.+?)}", r"(?P<_\1>.+)", pattern)
     result = re.search(regex, string)