add eslint disable prefix for prefer-arrow-callback rule on header of merge_request.js file

app/assets/javascripts/merge_request.js

-/* eslint-disable func-names, space-before-function-paren, no-var, space-before-blocks, prefer-rest-params, wrap-iife, quotes, no-underscore-dangle, one-var, one-var-declaration-per-line, consistent-return, dot-notation, quote-props, comma-dangle, object-shorthand, padded-blocks, max-len */
+/* eslint-disable func-names, space-before-function-paren, no-var, space-before-blocks, prefer-rest-params, wrap-iife, quotes, no-underscore-dangle, one-var, one-var-declaration-per-line, consistent-return, dot-notation, quote-props, comma-dangle, object-shorthand, padded-blocks, max-len, prefer-arrow-callback */
 /* global MergeRequestTabs */
 
 /*= require jquery.waitforimages */