tests: drop some obsolete py2 handling in util.py doctest
Flagged by PyCharm while inspecting imports from the platform modules.
--- a/mercurial/util.py Fri Dec 16 00:54:39 2022 -0500
+++ b/mercurial/util.py Fri Dec 16 14:15:09 2022 -0500
@@ -3213,10 +3213,7 @@
The passed argument is anything that has a ``.read(N)`` method.
- >>> try:
- ... from StringIO import StringIO as BytesIO
- ... except ImportError:
- ... from io import BytesIO
+ >>> from io import BytesIO
>>> uvarintdecodestream(BytesIO(b'\\x00'))
0
>>> uvarintdecodestream(BytesIO(b'\\x01'))