Web IDE: Remove redundant getter `hasChanges`
What does this MR do?
There is already a getter someUncommitedChanges that does the same
job, so replace it with that.
Also turns out that repo_tabs.vue doesn't really use the properties
hasChanges and mergeRequestId it takes in, so that resulted in a lot
of dead code removal.
These changes will make it easier to implement #196630 (closed).
References
Edited by Himanshu Kapoor