💄(frontend) remove course-glimpse background color

We recently revamp the HTML structure of the course glimpse but
 we forgot to remove the background color applied to the `.course-glimpse`
 element. This was invisible until the course glimpse was displayed on a
 background other than white...

Author: jbpenrath

src/frontend/scss/objects/_course_glimpses.scss

@@ -46,7 +46,6 @@ $course-glimpse-content-padding-sides: 0.7rem !default;
   // Apply card styles for elements
   @include m-o-card(
     $border: 0,
-    $background: r-theme-val(course-glimpse, card-background),
     $media-margin: 0,
     $wrapper-padding: 1.7rem $course-glimpse-content-padding-sides 0.5rem,
     $foot-divider: null