Update CHANGELOG.md for 10.7.6
Update CHANGELOG.md for 10.7.6

[ci skip]
mmkassem/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,dreampet/gitlab,stoplightio/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,dreampet/gitlab,dreampet/gitlab