Akuli and srittau: Remove Python 2 branches from Python 3 stubs (#5461)

* run script and do some manual changes (Akuli)

* do the whole thing manually (srittau)

* merge changes (Akuli)

Co-authored-by: Sebastian Rittau <srittau@rittau.biz>

stdlib/sndhdr.pyi

@@ -1,17 +1,14 @@
-import sys
 from _typeshed import AnyPath
-from typing import NamedTuple, Optional, Tuple, Union
+from typing import NamedTuple, Optional, Union
 
-if sys.version_info >= (3, 5):
-    class SndHeaders(NamedTuple):
-        filetype: str
-        framerate: int
-        nchannels: int
-        nframes: int
-        sampwidth: Union[int, str]
-    _SndHeaders = SndHeaders
-else:
-    _SndHeaders = Tuple[str, int, int, int, Union[int, str]]
+class SndHeaders(NamedTuple):
+    filetype: str
+    framerate: int
+    nchannels: int
+    nframes: int
+    sampwidth: Union[int, str]
+
+_SndHeaders = SndHeaders
 
 def what(filename: AnyPath) -> Optional[_SndHeaders]: ...
 def whathdr(filename: AnyPath) -> Optional[_SndHeaders]: ...