devel/got: update to 0.68

User-visible changes:

• apply time-based rate-limiting to send-/fetch-/index-pack progress output
• make the URI parser tolerate trailing slashes at the end of the input URI
• add 'got patch' command for applying unified diffs
• handle reference arguments which look like short object IDs
• make got log, diff, blame, tree, and cat unlock the work tree earlier
• print additional progress information while packing