ci: exclude the upstream g3 branch from building on CI (#32202)
ci: exclude the upstream g3 branch from building on CI (#32202)

We don't need to build this branch as it's informative for the purposes of figuring out
the diff between the master and what's synced into google3.

PR Close #32202

mprobst/angular,alexeagle/angular,ocombe/angular,mhevery/angular,JiaLiPassion/angular,alexeagle/angular,vikerman/angular,matsko/angular,angular-indonesia/angular,mgechev/angular,JiaLiPassion/angular,vikerman/angular,IdeaBlade/angular,brandonroberts/angular,vikerman/angular,wKoza/angular,blesh/angular,blesh/angular,vikerman/angular,Brocco/angular,alexeagle/angular,mhevery/angular,brandonroberts/angular,gnomeontherun/angular,StephenFluin/angular,matsko/angular,gnomeontherun/angular,angular/angular,wKoza/angular,alxhub/angular,gdi2290/angular,manekinekko/angular,snaptech/angular,manekinekko/angular,alxhub/angular,manekinekko/angular,gkalpak/angular,ocombe/angular,mhevery/angular,mprobst/angular,matsko/angular,Brocco/angular,matsko/angular,sarunint/angular,ocombe/angular,gdi2290/angular,shairez/angular,filipesilva/angular,snaptech/angular,filipesilva/angular,IdeaBlade/angular,shairez/angular,IdeaBlade/angular,angular-indonesia/angular,filipesilva/angular,Brocco/angular,shairez/angular,angular/angular,Brocco/angular,JiaLiPassion/angular,gkalpak/angular,alexeagle/angular,wKoza/angular,mprobst/angular,blesh/angular,gdi2290/angular,snaptech/angular,snaptech/angular,brandonroberts/angular,manekinekko/angular,wKoza/angular,Toxicable/angular,mgechev/angular,snaptech/angular,alxhub/angular,sarunint/angular,angular-indonesia/angular,gdi2290/angular,alexeagle/angular,Toxicable/angular,Toxicable/angular,sarunint/angular,mgechev/angular,gdi2290/angular,StephenFluin/angular,StephenFluin/angular,snaptech/angular,filipesilva/angular,shairez/angular,shairez/angular,alexeagle/angular,Brocco/angular,brandonroberts/angular,ocombe/angular,IdeaBlade/angular,wKoza/angular,vikerman/angular,mhevery/angular,vikerman/angular,Toxicable/angular,JiaLiPassion/angular,Brocco/angular,manekinekko/angular,ocombe/angular,alxhub/angular,gdi2290/angular,angular-indonesia/angular,blesh/angular,Toxicable/angular,gkalpak/angular,wKoza/angular,IdeaBlade/angular,gkalpak/angular,StephenFluin/angular,mhevery/angular,alxhub/angular,matsko/angular,mprobst/angular,sarunint/angular,filipesilva/angular,angular/angular,gnomeontherun/angular,mgechev/angular,gnomeontherun/angular,angular/angular,ocombe/angular,brandonroberts/angular,blesh/angular,StephenFluin/angular,sarunint/angular,brandonroberts/angular,Toxicable/angular,mgechev/angular,mprobst/angular,sarunint/angular,mprobst/angular,manekinekko/angular,mhevery/angular