Remove summarize diff quick action
What does this MR do and why?
Now that we automatically are generating the diff summary, we can remove the quick action.
The follow up clean up will be done in: #417113 (closed)
To Test:
On Master, check /summarize_diff comes with a popup
On this branch, cehck /summarize_diff does not come with a popup
Related Issue: #410208 (closed)
Edited by Marc Shaw