CrOS FilesApp remove unneeded crostini css important

The css !important is no longer needed since crostini is not
using the nassh FSP provided volume type.

Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I8a2803b934efbe7a1af8bbba0dd897987f28b3b7
Reviewed-on: https://chromium-review.googlesource.com/1139833
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575540}

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

@@ -458,18 +458,16 @@ cr-menu-item[command='#install-new-extension'] .icon.start {
 [file-type-icon='crostini'],
 [root-type-icon='crostini'],
 [volume-type-icon='crostini'] {
-  /* Need !important to override inline style applied to provided volumes. */
   background-image: -webkit-image-set(
       url(../images/volumes/linux_files.png) 1x,
-      url(../images/volumes/2x/linux_files.png) 2x) !important;
+      url(../images/volumes/2x/linux_files.png) 2x);
 }
 
 .tree-row[selected] [root-type-icon='crostini'],
 .tree-row[selected] [volume-type-icon='crostini'] {
-  /* Need !important to override inline style applied to provided volumes. */
   background-image: -webkit-image-set(
       url(../images/volumes/linux_files_active.png) 1x,
-      url(../images/volumes/2x/linux_files_active.png) 2x) !important;
+      url(../images/volumes/2x/linux_files_active.png) 2x);
 }
 
 [file-type-icon='android_files'],