wrapfunction: use sysstr instead of bytes as argument in "fsmonitor"

This is as valid and simpler, it will help us to eventually get ride of
`safehasattr`.

hgext/fsmonitor/__init__.py

@@ -755,9 +755,9 b' def extsetup(ui):'
     )
     if pycompat.isdarwin:
         # An assist for avoiding the dangling-symlink fsevents bug
-        extensions.wrapfunction(os, b'symlink', wrapsymlink)
+        extensions.wrapfunction(os, 'symlink', wrapsymlink)
 
-    extensions.wrapfunction(merge, b'_update', wrapupdate)
+    extensions.wrapfunction(merge, '_update', wrapupdate)
 
 
 def wrapsymlink(orig, source, link_name):