build: Update grunt-jscs devDependency to latest

grunt-jscs: 0.7.1 -> 0.8.1

No-op; note that this switches us from jscs 1.6.0 to 1.7.2, which provides
some new options (unused in the Wikimedia preset).

Change-Id: I1d0db2568ff673ff8b8bba9549b06c005eb7186b