package.json - fix repo url
package.json - fix repo url

https://gerrit.wikimedia.org/r/oojs/core doesn't work
Shown as the repository link at https://www.npmjs.com/package/oojs

Change-Id: I31c35083e81d477d910c8da5749c08152e14ac64

wikimedia/oojs,wikimedia/oojs