Update EE downgrade instructions to include JenkinsDeprecatedService
Update EE downgrade instructions to include JenkinsDeprecatedService

Closes #19133

[ci skip]

t-zuehlsdorff/gitlabhq,t-zuehlsdorff/gitlabhq,darkrasid/gitlabhq,SVArago/gitlabhq,shinexiao/gitlabhq,martijnvermaat/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,htve/GitlabForChinese,openwide-java/gitlabhq,daiyu/gitlab-zh,openwide-java/gitlabhq,daiyu/gitlab-zh,LUMC/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,stoplightio/gitlabhq,t-zuehlsdorff/gitlabhq,mmkassem/gitlabhq,dplarson/gitlabhq,dreampet/gitlab,SVArago/gitlabhq,mmkassem/gitlabhq,openwide-java/gitlabhq,t-zuehlsdorff/gitlabhq,mr-dxdy/gitlabhq,LUMC/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,mr-dxdy/gitlabhq,mr-dxdy/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,martijnvermaat/gitlabhq,martijnvermaat/gitlabhq,jirutka/gitlabhq,htve/GitlabForChinese,icedwater/gitlabhq,martijnvermaat/gitlabhq,iiet/iiet-git,shinexiao/gitlabhq,axilleas/gitlabhq,screenpages/gitlabhq,mr-dxdy/gitlabhq,iiet/iiet-git,htve/GitlabForChinese,dplarson/gitlabhq,allysonbarros/gitlabhq,htve/GitlabForChinese,dreampet/gitlab,screenpages/gitlabhq,mmkassem/gitlabhq,SVArago/gitlabhq,LUMC/gitlabhq,SVArago/gitlabhq,screenpages/gitlabhq,dplarson/gitlabhq,darkrasid/gitlabhq,shinexiao/gitlabhq,dplarson/gitlabhq,daiyu/gitlab-zh,allysonbarros/gitlabhq,openwide-java/gitlabhq,jirutka/gitlabhq,LUMC/gitlabhq,stoplightio/gitlabhq,icedwater/gitlabhq,darkrasid/gitlabhq,dreampet/gitlab,daiyu/gitlab-zh,icedwater/gitlabhq,shinexiao/gitlabhq,screenpages/gitlabhq,jirutka/gitlabhq,icedwater/gitlabhq,allysonbarros/gitlabhq,darkrasid/gitlabhq,allysonbarros/gitlabhq,axilleas/gitlabhq,iiet/iiet-git