Update CHANGELOG.md for 12.0.6
Update CHANGELOG.md for 12.0.6

[ci skip]
stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq