Correct previous stable branch used in 8.14 to 8.15 update guide
Correct previous stable branch used in 8.14 to 8.15 update guide

[ci skip]

iiet/iiet-git,stoplightio/gitlabhq,htve/GitlabForChinese,dplarson/gitlabhq,openwide-java/gitlabhq,darkrasid/gitlabhq,axilleas/gitlabhq,dplarson/gitlabhq,dplarson/gitlabhq,openwide-java/gitlabhq,dreampet/gitlab,dreampet/gitlab,t-zuehlsdorff/gitlabhq,dreampet/gitlab,openwide-java/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,t-zuehlsdorff/gitlabhq,jirutka/gitlabhq,htve/GitlabForChinese,axilleas/gitlabhq,t-zuehlsdorff/gitlabhq,darkrasid/gitlabhq,LUMC/gitlabhq,dplarson/gitlabhq,htve/GitlabForChinese,LUMC/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,stoplightio/gitlabhq,htve/GitlabForChinese,LUMC/gitlabhq,t-zuehlsdorff/gitlabhq,darkrasid/gitlabhq,iiet/iiet-git,LUMC/gitlabhq,openwide-java/gitlabhq,iiet/iiet-git,darkrasid/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq