docs(CHANGES): Note test tweaks

Author: tony

CHANGES

@@ -27,6 +27,8 @@ $ pipx install --suffix=@next 'tmuxp' --pip-args '\--pre' --force
 
 - {issue}`777` Fix {issue}`778` to move the old, broken `retry()` to the new
   `retry_until()`, credit: @categulario.
+- {issue}`781` Testing with ZSH will mock `~/.zshrc` startup file for cleaner
+  pane outputs.
 
 ## tmuxp 1.11.1 (2022-05-02)