Update mocha requirement from ^2.3.3 to ^6.1.4#1

dependabot-preview[bot] wants to merge 1 commit intomasterfixjs/deferred.js:masterfrom

dependabot/npm_and_yarn/mocha-tw-6.1.4fixjs/deferred.js:dependabot/npm_and_yarn/mocha-tw-6.1.4Copy head branch name to clipboard