Fix UPGRADE.txt Due To Merging From Branch 11

When merging in the patch for ASTERISK-22728, the UPGRADE.txt file was changed
incorrectly.  That change should have gone into ASTERISK-11.txt.

This commit is to fix that.

Also, another comment in the UPGRADE-11.txt was missing and this commit adds
that as well.
........

Merged revisions 402115 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@402117 65c4cc65-6c06-0410-ace0-fbb531ad65f3