cmd/auth/cookieauth: delete unreachable os.Exit

Change-Id: I5c60eeb8667423544b2bc8b9cf5f51279b0a941d
GitHub-Last-Rev: cb0eca5
GitHub-Pull-Request: #388
Reviewed-on: https://go-review.googlesource.com/c/tools/+/418854
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

cmd/auth/cookieauth/cookieauth.go

@@ -40,7 +40,6 @@ func main() {
 	f, err := os.Open(os.Args[1])
 	if err != nil {
 		log.Fatalf("failed to read cookie file: %v\n", os.Args[1])
-		os.Exit(1)
 	}
 	defer f.Close()