GitLens isn't respecting date time format

[justinrobots]

GitLens is not respecting gitlens.graph.dateFormat": "YYYY/MM/DD

Reported by @nzaytsev

Upd. In case of not selected "gitlens.graph.dateStyle": "absolute"

[nzaytsev]

Maybe it's not a bug, but an additional tips required. We need to warn that the format is not considered in case of default(relative) style