Remove unneeded Vue require statements.

app/assets/javascripts/issuable/time_tracking/time_tracking_bundle.js.es6

-//= require vue
 //= require ./components/time_tracker
 //= require smart_interval
 //= require subbable_resource

app/assets/javascripts/merge_conflicts/merge_conflicts_bundle.js.es6

 /* eslint-disable */
-//= require vue
 //= require ./merge_conflict_store
 //= require ./merge_conflict_service
 //= require ./mixins/line_conflict_utils