The dev gave directions in the gitlab issue above for reassigning the keybinding. It didn't work for me. This sort of does: https://stackoverflow.com/questions/59240244/disable-changing-default-keyboard-shortcuts-in-iterm2
Specifically that gives directions for configuring the OS to use a different keybinding for that menu option in that app. I didn't see an obvious way to use that screen to completely disable the keybinding.

Mostly I'm working around this by changing my muscle memory to the grow font size on my work Mac until I can acclimate to a better terminal.