Fix missing credential error message

LOAS credential enforcement is already taking effect, not in the future.
Update the warning message accordingly.

Test: gcertdestroy && m and inspect error message
Bug: 318506452
Change-Id: I857f44b265c454beaffb9e662bd318aeb29f6cdb
diff --git a/ui/build/rbe.go b/ui/build/rbe.go
index fa04207..5142a41 100644
--- a/ui/build/rbe.go
+++ b/ui/build/rbe.go
@@ -163,7 +163,7 @@
 		return
 	}
 	fmt.Fprintln(ctx.Writer, "")
-	fmt.Fprintln(ctx.Writer, "\033[33mWARNING: Missing LOAS credentials, please run `gcert`. This will result in failing builds in the future, see go/rbe-android-default-announcement.\033[0m")
+	fmt.Fprintln(ctx.Writer, "\033[33mWARNING: Missing LOAS credentials, please run `gcert`. This is required for a successful build execution. See go/rbe-android-default-announcement for more information.\033[0m")
 	fmt.Fprintln(ctx.Writer, "")
 }