mypy fixup

Author: jbrockmendel

pandas/core/arrays/string_arrow.py

@@ -280,7 +280,6 @@ def astype(self, dtype, copy: bool = True):
     # String methods interface
 
     _str_map = BaseStringArray._str_map
-    _str_find = ArrowExtensionArray._str_find
 
     def _str_contains(
         self, pat, case: bool = True, flags: int = 0, na=np.nan, regex: bool = True