ci: avoid testing angular.io against RxJS v7 twice (#43767)
ci: avoid testing angular.io against RxJS v7 twice (#43767)

Previously, we used to run the angular.io unit tests against both RxJS
v6 (which was the version specified in `package.json`) and RxJS v7 on
CI, as a way to guard against future regressions with RxJS v7.

Now that `package.json` has been updated to RxJS v7, there is no reason
to explicitly re-run the unit test against RxJS v7 on CI, so this commit
removes the corresponding steps.

PR Close #43767

gkalpak/angular,brandonroberts/angular,angular/angular,gnomeontherun/angular,ocombe/angular,angular-indonesia/angular,shairez/angular,shairez/angular,brandonroberts/angular,manekinekko/angular,manekinekko/angular,manekinekko/angular,shairez/angular,angular/angular,ocombe/angular,gnomeontherun/angular,gkalpak/angular,angular-indonesia/angular,angular/angular,manekinekko/angular,ocombe/angular,gkalpak/angular,manekinekko/angular,JiaLiPassion/angular,angular-indonesia/angular,brandonroberts/angular,brandonroberts/angular,shairez/angular,ocombe/angular,brandonroberts/angular,brandonroberts/angular,ocombe/angular,ocombe/angular,gnomeontherun/angular,JiaLiPassion/angular,angular/angular,JiaLiPassion/angular,shairez/angular,gkalpak/angular,angular-indonesia/angular,gnomeontherun/angular,manekinekko/angular,JiaLiPassion/angular