screentest: enable test x/tools directories expanded

This will be useful for https://go.dev/cl/620739 --
https://go.dev/cl/413680 (the CL that disabled it) says it was failing
on the CI, maybe we'll have better luck this time?
I'd like to enable it here so cl/620739 can capture the diff.

Change-Id: Id0000000c68af80d5194e955e0df7df59f58f29d
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/624475
Run-TryBot: Jonathan Amsterdam <[email protected]>
kokoro-CI: kokoro <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: avamsi

tests/screentest/testcases.txt

@@ -33,14 +33,14 @@ eval {{$hideElements}}
 capture viewport
 capture viewport 540x1080
 
-# test x/tools directories expanded
-# pathname /golang.org/x/[email protected]
-# wait {{$ready}}
-# click [data-test-id="directories-toggle"]
-# eval {{$scrollTop}}
-# eval {{$hideElements}}
-# capture fullscreen
-# capture fullscreen 540x1080
+test x/tools directories expanded
+pathname /golang.org/x/[email protected]
+wait {{$ready}}
+click [data-test-id="directories-toggle"]
+eval {{$scrollTop}}
+eval {{$hideElements}}
+capture fullscreen
+capture fullscreen 540x1620
 
 # TODO: https://go.dev/issue/51020
 # test empty jump to modal