Drop Python 2 support from python-gflags (#7709)

stubs/python-gflags/METADATA.toml

@@ -1,2 +1 @@
 version = "3.1.*"
-python2 = true

stubs/python-gflags/gflags.pyi

@@ -1,5 +1,6 @@
+from collections.abc import Callable, Iterable, Sequence
 from types import ModuleType
-from typing import IO, Any, Callable, Iterable, Sequence, Text
+from typing import IO, Any
 
 class Error(Exception): ...
 
@@ -123,7 +124,7 @@ class Flag:
     def Type(self) -> str: ...
     def WriteInfoInXMLFormat(self, outfile: IO[str], module_name: str, is_key: bool = ..., indent: str = ...) -> None: ...
 
-class ArgumentParser(object):
+class ArgumentParser:
     syntactic_help: str
     # TODO what is this
     def parse(self, argument: Any) -> Any: ...
@@ -133,7 +134,7 @@ class ArgumentParser(object):
     def WriteCustomInfoInXMLFormat(self, outfile: IO[str], indent: str) -> None: ...
 
 class ArgumentSerializer:
-    def Serialize(self, value: Any) -> Text: ...
+    def Serialize(self, value: Any) -> str: ...
 
 class ListSerializer(ArgumentSerializer):
     def __init__(self, list_sep: str) -> None: ...