Revert 4932

http://manage.dimagi.com/default.asp?149247

Revert "pull out migration-related styles into separate file so that core styles can be used in new static site"

This reverts commit ea102e666c5453897828e8561a2152a3358da0d8. (on PR https://github.com/dimagi/commcare-hq/pull/4932)
@biyeun