Drop wrong variable annotations in BlobFilter.__call__

This fixes two mypy errors by removing the annotations of the
filter_parts and blob_parts local variables as lists. They only
need to be sequences (more precisely, they only need to be sized
and iterable, they don't even need to support subscripting in the
way __call__ uses them), and mypy is able to infer their type.

Author: EliahKagan

git/index/typ.py

@@ -12,7 +12,7 @@
 
 # typing ----------------------------------------------------------------------
 
-from typing import NamedTuple, Sequence, TYPE_CHECKING, Tuple, Union, cast, List
+from typing import NamedTuple, Sequence, TYPE_CHECKING, Tuple, Union, cast
 
 from git.types import PathLike
 
@@ -60,8 +60,8 @@ def __call__(self, stage_blob: Tuple[StageType, Blob]) -> bool:
             path: Path = pathlike if isinstance(pathlike, Path) else Path(pathlike)
             # TODO: Change to use `PosixPath.is_relative_to` once Python 3.8 is no
             # longer supported.
-            filter_parts: List[str] = path.parts
-            blob_parts: List[str] = blob_path.parts
+            filter_parts = path.parts
+            blob_parts = blob_path.parts
             if len(filter_parts) > len(blob_parts):
                 continue
             if all(i == j for i, j in zip(filter_parts, blob_parts)):