Resolved comment showing up in Files Changed tab

[kuychaco]

This comment lives in the fake PR we use for UXR studies -- #1919

Tested using a local build of Atom with github@v0.25.0-0 pre-release. atom/atom#18787, commit b83bd8f

[annthurium]

should be resolved by RCID stuff, because we no longer show the comment, just a decoration and it's ok to have decorations for unresolved comments.