Remove package-lock.json from .gitignore.
Remove package-lock.json from .gitignore.

Change-Id: Id798eaabd95f5fc1bc5c98cec802213552c551d8
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/269856
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot