Files app: Fix selection outline on grid view

Basically the same idea of CL:1672612, change the style of the
currently focused element to *not* have outline.

Again, Claire approves! :-)

Bug: 977534
Change-Id: I8fde098f93db2134d2e64d063c182effd0884a74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1677389
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672437}

ui/file_manager/file_manager/foreground/css/file_manager.css

@@ -1259,10 +1259,6 @@ body[type='full-page'] .detail-name .detail-icon {
   background-color: rgba(51, 103, 214, 0.2);
 }
 
-body.check-select .thumbnail-grid:focus .thumbnail-item[lead] {
-  outline: 1px solid rgba(51, 103, 214, 0.5);
-}
-
 .thumbnail-grid .checkmark {
   background-position: center;
   background-repeat: no-repeat;