docs: update latest angular version referenced in docs
docs: update latest angular version referenced in docs

Update upgrade guide to reference version 9 as the latest angular version
catull/angular-cli,geofffilippi/angular-cli,angular/angular-cli,beeman/angular-cli,clydin/angular-cli,angular/angular-cli,beeman/angular-cli,catull/angular-cli,manekinekko/angular-cli,geofffilippi/angular-cli,filipesilva/angular-cli,filipesilva/angular-cli,manekinekko/angular-cli,angular/angular-cli,angular/angular-cli,catull/angular-cli,Brocco/angular-cli,Brocco/angular-cli,Brocco/angular-cli,ocombe/angular-cli,clydin/angular-cli,clydin/angular-cli,geofffilippi/angular-cli,Brocco/angular-cli,filipesilva/angular-cli,geofffilippi/angular-cli,filipesilva/angular-cli,beeman/angular-cli,ocombe/angular-cli,beeman/angular-cli,Brocco/angular-cli,manekinekko/angular-cli,ocombe/angular-cli,ocombe/angular-cli,clydin/angular-cli,ocombe/angular-cli,catull/angular-cli