Revert bigframes/dtypes.py and mypy.ini to main branch version

Author: shuoweil

bigframes/dtypes.py

@@ -972,21 +972,6 @@ def contains_db_dtypes_json_dtype(dtype):
     return contains_db_dtypes_json_arrow_type(dtype.pyarrow_dtype)
 
 
-def _replace_json_arrow_with_string(pa_type: pa.DataType) -> pa.DataType:
-    """Recursively replace JSONArrowType with string type."""
-    if isinstance(pa_type, db_dtypes.JSONArrowType):
-        return pa.string()
-    if isinstance(pa_type, pa.ListType):
-        return pa.list_(_replace_json_arrow_with_string(pa_type.value_type))
-    if isinstance(pa_type, pa.StructType):
-        new_fields = [
-            field.with_type(_replace_json_arrow_with_string(field.type))
-            for field in pa_type
-        ]
-        return pa.struct(new_fields)
-    return pa_type
-
-
 def warn_on_db_dtypes_json_dtype(dtypes):
     """Warn that the JSON dtype is changing.
 

mypy.ini

@@ -44,6 +44,3 @@ ignore_missing_imports = True
 
 [mypy-anywidget]
 ignore_missing_imports = True
-
-[mypy-db_dtypes]
-ignore_missing_imports = True