devel/got: update to 0.53

User-visible changes:

• add a gotadmin utility with info, pack, indexpack, and listpack commands
• do not update symlinks which are already up-to-date
• fix 3-way merge of files which lack a final \n
• avoid an error in tog(1) while the terminal window is being resized
• catch invalid reference names passed to 'got ref -l'
• fix unrelated changes being merged by got cherrypick/backout/rebase/histedit
• new -I option for 'got status' to show files which match an ignore pattern