Marking commits for 2.5.1

In BIT-1763, Johanna asks for a way to mark commits for a point
release (assuming we do one). Let's do this: set the "fix version" of
the ticket to include 2.5.1 and add the commit hash for the fix to the
notes. Then we can later search for these and cherry-pick. (We'll
still close the ticket once fixed in master to avoid confusion.)