docs: change function name from async -> waitForAsync (#38548)
docs: change function name from async -> waitForAsync (#38548)

async function name was changed to waitForAsync but it was left in testing-utility-api
file.

PR Close #38548

gnomeontherun/angular,manekinekko/angular,angular-indonesia/angular,brandonroberts/angular,gkalpak/angular,wKoza/angular,JiaLiPassion/angular,angular/angular,gnomeontherun/angular,ocombe/angular,IdeaBlade/angular,mgechev/angular,manekinekko/angular,mgechev/angular,gkalpak/angular,mgechev/angular,brandonroberts/angular,alxhub/angular,blesh/angular,alxhub/angular,gnomeontherun/angular,gkalpak/angular,wKoza/angular,angular/angular,brandonroberts/angular,shairez/angular,brandonroberts/angular,brandonroberts/angular,mgechev/angular,mgechev/angular,IdeaBlade/angular,manekinekko/angular,JiaLiPassion/angular,JiaLiPassion/angular,shairez/angular,alxhub/angular,shairez/angular,manekinekko/angular,wKoza/angular,wKoza/angular,angular-indonesia/angular,blesh/angular,gkalpak/angular,ocombe/angular,shairez/angular,IdeaBlade/angular,blesh/angular,ocombe/angular,ocombe/angular,JiaLiPassion/angular,wKoza/angular,shairez/angular,manekinekko/angular,gnomeontherun/angular,blesh/angular,manekinekko/angular,angular/angular,IdeaBlade/angular,ocombe/angular,ocombe/angular,blesh/angular,angular-indonesia/angular,alxhub/angular,IdeaBlade/angular,angular/angular,brandonroberts/angular,alxhub/angular,wKoza/angular,angular-indonesia/angular