[migration/3.18] Explicitly delete constraint on defaultval
Make sure the SizeConstraint on defaultval is removed, and avoid more
unnecessary commits.
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')