BUG FIX: to_json() with JSON Table Schema work correctly with string dtype.

[khemkaran10]

Fixes: #61889

To ensure consistent behavior for to_json(), when dtype="str" is used, it will now output "type": "string" instead of "type": "any".

Before Fix:

>>> pd.Series(["a", "b", None], dtype="str").to_json(orient="table", index=False)
'{"schema":{"fields":[{"name":"values","type":"any","extDtype":"str"}],"pandas_version":"1.4.0"},"data":[{"values":"a"},{"values":"b"},{"values":null}]}'

After Fix:

>>> pd.Series(["a", "b", None], dtype="str").to_json(orient="table", index=False)
'{"schema":{"fields":[{"name":"values","type":"string","extDtype":"str"}],"pandas_version":"1.4.0"},"data":[{"values":"a"},{"values":"b"},{"values":null}]}'

• closes BUG: make to_json with JSON Table Schema work correctly with string dtype #61889
• 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.