change empty bodies from "pass" to "..."

CONTRIBUTING.md says to prefer ... Not the most impactful change but fixing
these will allow us to lint for it in the future and get a consistent style.

stdlib/2/encodings/utf_8.pyi

@@ -9,6 +9,6 @@ class StreamWriter(codecs.StreamWriter):
 class StreamReader(codecs.StreamReader):
     pass
 
-def getregentry() -> codecs.CodecInfo: pass
-def encode(input: str, errors: str = ...) -> bytes: pass
-def decode(input: bytes, errors: str = ...) -> str: pass
+def getregentry() -> codecs.CodecInfo: ...
+def encode(input: str, errors: str = ...) -> bytes: ...
+def decode(input: bytes, errors: str = ...) -> str: ...