docs(dev-infra): add instructions for updating GeckoDriver in `browsers/README.md` (#40150)
docs(dev-infra): add instructions for updating GeckoDriver in `browsers/README.md` (#40150)

This commit adds instructions in `dev-infra/browsers/README.md` on how
to update the version of GeckoDriver (the WebDriver implementation for
Firefox browsers).

NOTE:
The gecko driver download URLs perform redirection, so the `curl`
command needs to be run with the `-L/--location` option to follow
redirects. I updated all `curl` commands (even those that are not used
on gecko driver download URLs) for consistency.

PR Close #40150

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