yarn: Add integrity hashes back to yarn.lock.
yarn: Add integrity hashes back to yarn.lock.

These were lost in 8650a7b93.  Probably this was a mismerge
when rebasing a branch from before ed976d85d added these in
the first place.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile