Disable globalShortcut spec on Windows CI

[kevinsawicki]

Looks to be failing consistently, disabling while I investigate further, introduced in #6787 🔴

not ok 147 globalShortcut module can register and unregister accelerators
  AssertionError: false == true
      at Context.it (C:\Jenkins\workspace\electron-win-x64\spec\api-global-shortcut-spec.js:14:12)
      at callFn (C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runnable.js:251:21)
      at Test.Runnable.run (C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runnable.js:244:7)
      at Runner.runTest (C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runner.js:374:10)
      at C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runner.js:452:12
      at next (C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runner.js:299:14)
      at C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runner.js:309:7
      at next (C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runner.js:248:23)
      at C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runner.js:271:7
      at done (C:\Jenkins\workspace\electron-win-x64\spec\node_modules\mocha\lib\runnable.js:207:5)