fix: reference to SendClientSideEvent

[mattkrick]

Description

fixes borked master

From slack rant:

master is broken right now! It looks like our GitHub strategy is to blame:
The error is Can't resolve '../mutations/SendClientSideEvent'
This is because #9067 changed the location of that file
And #9057 referenced the old location
The root cause is that we don’t require PRs be brought up to date before we allow them to be merged. For example, I open a PR, the checks pass, someone else’s PR gets merged which would cause my PR to break, but since my checks already passed, I can merge & break master