Remove StringArrayTypes type hint

Reverts 0a6cda5, f59f93c, and 17c1e9c

Author: weiji14

pygmt/_typing.py

@@ -2,17 +2,7 @@
 Type aliases for type hints.
 """
 
-import contextlib
-import importlib
-from collections.abc import Sequence
 from typing import Literal
 
-import numpy as np
-
 # Anchor codes
 AnchorCode = Literal["TL", "TC", "TR", "ML", "MC", "MR", "BL", "BC", "BR"]
-
-# String array types
-StringArrayTypes = Sequence[str] | np.ndarray
-with contextlib.suppress(ImportError):
-    StringArrayTypes |= importlib.import_module(name="pyarrow").StringArray