fix: use arrow backend for "\\d" replacements

Author: Alvaro-Kothe

pandas/core/arrays/_arrow_string_mixins.py

@@ -173,15 +173,12 @@ def _str_replace(
             or callable(repl)
             or not case
             or flags
-            or (
-                isinstance(repl, str)
-                and r"\g<" in repl  # Block named group references (\g<name>); numeric groups (\1) are supported by PyArrow
-            )
+            or (isinstance(repl, str) and r"\g<" in repl)
         ):
             raise NotImplementedError(
                 "replace is not supported with a re.Pattern, callable repl, "
                 "case=False, flags!=0, or when the replacement string contains "
-                "named group references (\\g<...>, \\d+)"
+                "named group references (\\g<...>)"
             )
 
         func = pc.replace_substring_regex if regex else pc.replace_substring

pandas/core/arrays/string_arrow.py

@@ -425,8 +425,7 @@ def _str_replace(
             or flags
             or (  # substitution contains a named group pattern
                 # https://docs.python.org/3/library/re.html
-                isinstance(repl, str)
-                and (r"\g<" in repl or re.search(r"\\\d", repl) is not None)
+                isinstance(repl, str) and r"\g<" in repl
             )
         ):
             return super()._str_replace(pat, repl, n, case, flags, regex)