[1.7.x] Fixed #22458 -- Added a note about MySQL utf8_unicode_ci collation
[1.7.x] Fixed #22458 -- Added a note about MySQL utf8_unicode_ci collation

Thanks tobami at gmail.com for the report.

Backport of 11ac50b18e from master

oscaro/django,oscaro/django,jyotsna1820/django,jyotsna1820/django,jyotsna1820/django,oscaro/django,oscaro/django,jyotsna1820/django