update-oojs.sh: Rewrite to fetch from npm repo instead of building from git

* Fetch upstream build from npm repository instead of building it locally
  from git (to avoid different timestamps and checksums not matching, no
  need for MediaWiki code to know how to build a oojs distribution).

* Ran it which changed the oojs.js file slightly (it now contains the file
  as released on npmjs.org instead of the local build by the person who
  last updated it in mediawiki).

Follows-up:
* 648667a - Split up resources/ into resources/lib/ and resources/src/
* c68b967 - Add scripts to generate update builds of OOjs

Change-Id: I63f79293e21781c1db3d7c43658c22f58ba9102d
Merge "update-oojs.sh: Rewrite to fetch from npm repo instead of building from git"