DEV: patchbot: only display the first 8 chars of the commit id

DEV: patchbot: only display the first 8 chars of the commit id

The commit id column doesn't need to show more than 8 chars to stay
unambiguous within a single page, and longer ids needlessly widen the
table. Everything that is keyed on the id (the commit link, the row's
name= attribute and the cid[] JS array) keeps the full id produced by
the pipeline, whatever its length, so this is a display-only change
which also gets us ready for a possible future move of the pipeline to
longer ids.