BUG: Fix TypeError in json_normalize with non-str meta key and record_path

[dongwonmoon]

• closes BUG: pd.json_normalize has inconsistent validation for non-string keys - accepts integers in some parameter combinations but rejects in others #63019 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[dongwonmoon]

Hi reviewers,

P.S. While working on this fix, I noticed that the type hint for the meta parameter is currently specified as str | list[str | list[str]].

My PR ensures that non-string keys (like the int key in our test case) are handled consistently, whether record_path is specified or not. This aligns with the existing behavior when record_path=None, which already supports non-string keys (mirroring pd.DataFrame's ability to have non-string column names).

I've kept this PR scoped strictly to fixing the TypeError and ensuring consistent behavior.

Would a separate, follow-up issue or PR to discuss updating the type hint (perhaps to something like Hashable or Any) to match this behavior be welcome? Just wanted to bring it to your attention.

Thanks!