clean python 3 specific stuff from stdlib/@python2 stubs (#5451)

stdlib/@python2/webbrowser.pyi

@@ -3,16 +3,9 @@ from typing import Callable, List, Optional, Sequence, Text, Union
 
 class Error(Exception): ...
 
-if sys.version_info >= (3, 7):
-    def register(
-        name: Text, klass: Optional[Callable[[], BaseBrowser]], instance: Optional[BaseBrowser] = ..., *, preferred: bool = ...
-    ) -> None: ...
-
-else:
-    def register(
-        name: Text, klass: Optional[Callable[[], BaseBrowser]], instance: Optional[BaseBrowser] = ..., update_tryorder: int = ...
-    ) -> None: ...
-
+def register(
+    name: Text, klass: Optional[Callable[[], BaseBrowser]], instance: Optional[BaseBrowser] = ..., update_tryorder: int = ...
+) -> None: ...
 def get(using: Optional[Text] = ...) -> BaseBrowser: ...
 def open(url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
 def open_new(url: Text) -> bool: ...