fix(nwis): parameterize _reject_unexpected_format kwargs for mypy --strict

`kwargs: dict` tripped mypy's disallow-any-generics under the strict
type-check CI, which runs against the PR merged into main. Annotate it as
`dict[str, object]` -- a builtin generic that needs no `typing` import, so it
stays ruff-clean on this branch (which predates main's `from typing import
Any`) and avoids an add/add conflict on that import line when merged.

Verified: mypy --strict and ruff both clean on the merge with main; the nwis
suite (57) still passes.

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

Author: t

dataretrieval/nwis.py

@@ -130,7 +130,9 @@ def _parse_json_or_raise(response: httpx.Response) -> pd.DataFrame:
         raise
 
 
-def _reject_unexpected_format(kwargs: dict, func_name: str, expected: str) -> None:
+def _reject_unexpected_format(
+    kwargs: dict[str, object], func_name: str, expected: str
+) -> None:
     """Drop ``format`` from ``kwargs`` and reject any value other than ``expected``.
 
     These getters always request a fixed ``format`` and parse that specific body,