[1.2.X] Fixed grammar and tweaked notes about MySQL database/table collation...

[1.2.X] Fixed grammar and tweaked notes about MySQL database/table collation interaction with text fields. Refs #14417.

Backport of [14779] from trunk

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14780 bcc190cf-cafb-0310-a4f2-bffc1f526a37