activities-rename in activities-tabs-mode should rename the activity tab immediately

As it stands, one has to wait for what seems like 5 seconds before the tab name changes after ```activities-rename```. It doesn't seem related to ```activities-mode-idle-frequency``` as I set it to 1 second and still had to wait 5. I can see that the mode-line updates immediately, but not the tab bar. It's probably obvious why, but perhaps waking before 5am for the solstice sunrise has addled my brain today.