fix(gfql/cudf): py3.8/3.9 typing — Tuple[...] not builtin tuple[...] in _cudf_regex_prep

The cuDF =~ flags commit annotated _cudf_regex_prep with "tuple[object, bool]",
which mypy rejects on py3.8/3.9 (builtin generics need 3.9+/3.10+); broke the
python-lint-types (3.8, 3.9) lanes on #1675/#1677. Use typing.Tuple.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: lmeyerov

graphistry/compute/predicates/str.py

@@ -1,4 +1,4 @@
-from typing import Any, Optional, Union, cast
+from typing import Any, Optional, Tuple, Union, cast
 import re
 
 import pandas as pd
@@ -424,7 +424,7 @@ def _validate_fields(self) -> None:
             )
 
 
-def _cudf_regex_prep(pat: object, case: bool) -> "tuple[object, bool]":
+def _cudf_regex_prep(pat: object, case: bool) -> Tuple[object, bool]:
     """Adapt a regex for libcudf, which rejects inline flag groups (``(?i)``,
     ``(?m)``, ``(?s)`` …) at ANY position (raises "invalid regex pattern").