pyupgrade: drop redundant `open()` modes On one hand, this gets rid of some py2 cruft (like `U` and `t` modes). OTOH, I like being explict. But there's no way to disable individual transformations (and this change is part of `_fix_tokens()`, which is even harder to selectively use locally), and I'd rather have less noise when using `pyupgrade`. Warning: `contrib/synthrepo.py` appears not to have been updated to py3, as it's passing str to `error.Abort`. But since it was opening the file in unicode on py2, this change is a no-op.

--- a/contrib/perf-utils/perf-revlog-write-plot.py	Mon Jan 06 01:44:46 2025 -0500
+++ b/contrib/perf-utils/perf-revlog-write-plot.py	Tue Jan 07 17:28:46 2025 -0500
@@ -118,7 +118,7 @@
 
     if len(sys.argv) > 1:
         print('reading from %r' % sys.argv[1])
-        with open(sys.argv[1], 'r') as fp:
+        with open(sys.argv[1]) as fp:
             plot(json.load(fp), title=sys.argv[1])
     else:
         print('reading from stdin')