Docs: Use jest.setTimeout instead of jasmine timeout (#562)

* Use jest.setTimeout instead of jasmine timeout

Since jest@20 or so [jest.setTimeout](https://facebook.github.io/jest/docs/en/jest-object.html#jestsettimeouttimeout) is available, instead of jasmine-specific timeout constant.

* Adjust commit

* Adjust wording

docs/Guide.Jest.md

@@ -25,8 +25,8 @@ You should remove `e2e/mocha.opts`, you no longer need it.
 const detox = require('detox');
 const config = require('../package.json').detox;
 
-// Set the default timeout
-jasmine.DEFAULT_TIMEOUT_INTERVAL = 120000;
+// Set the default test timeout of 120s
+jest.setTimeout(120000);
 
 beforeAll(async () => {
   await detox.init(config);