docs(CHANGES): Server repr names the socket it uses

what:
- Record the repr fix under `Fixes`.

Author: tony

CHANGES

@@ -45,6 +45,11 @@ $ uvx --from 'libtmux' --prerelease allow python
 _Notes on the upcoming release will go here._
 <!-- END PLACEHOLDER - ADD NEW CHANGELOG ENTRIES BELOW THIS LINE -->
 
+### Fixes
+
+- {class}`~libtmux.Server` now reprs the socket path tmux resolves from
+  `$TMUX_TMPDIR` instead of a hard-coded `/tmp/tmux-<euid>/default` (#723)
+
 ### Documentation
 
 #### Cleaner `from_env` examples (#719)