Files.app: Remove hover effect from toolbar buttons.

BUG=461668
TEST=manually checked

Review URL: https://codereview.chromium.org/967513003

Cr-Commit-Position: refs/heads/master@{#318848}

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

@@ -301,16 +301,12 @@ body.check-select .dialog-header .icon-button paper-ripple {
   rgb(90, 90, 90);
 }
 
-.dialog-header .icon-button:hover,
 .dialog-header .icon-button:focus,
-.dialog-header .combobutton:hover,
 .dialog-header .combobutton:focus {
   background-color: rgba(90, 90, 90, 0.15);
 }
 
-body.check-select .dialog-header .icon-button:hover,
 body.check-select .dialog-header .icon-button:focus,
-body.check-select .dialog-header .combobutton:hover,
 body.check-select .dialog-header .combobutton:focus {
   background-color: rgba(153, 153, 153, 0.20);
 }