Notification or banner when diff limits are reached in the Merge Request
### Problem to solve
Its not obvious to users when the diff limit has been reached.
### Intended users
* Delaney (Development Team Lead)
* Sasha (Software Developer)
### Proposal
There should be some kind of obvious banner or notification (probably within the Changes tab in the MR) that the diff limit has been reached/exceeded.
### Permissions and Security
Anyone who is able to view the MR diffs should be able to see this.
### What does success look like, and how can we measure that?
If a user can easily see that the diff limit has been reached in the MR.
### Links / references
issue