Merge pull request #5824 from edx/sarina/remove-unused-lms_static_images

Remove unused images from lms/static/images

lms/static/sass/base/_variables.scss

@@ -405,7 +405,7 @@ $login-banner-image: url(../images/bg-banner-account.png);
 $register-banner-image: url(../images/bg-banner-account.png);
 $passwordreset-banner-image: url(../images/bg-banner-account.png);
 
-$video-thumb-url: '../images/courses/video-thumb.jpg';
+$video-thumb-url: '../images/homepage-hero-video-thumb.jpg';
 
 // ====================
 

lms/static/sass/course/discussion/_form-wmd-toolbar.scss

@@ -52,7 +52,7 @@
   margin-left: 5px;
   margin-right: 5px;
   position: absolute;
-  background-image: url(../images/askbot/wmd-buttons.png);
+  background-image: url(../images/wmd-buttons.png);
   background-repeat: no-repeat;
   background-position: 0px 0px;
   display: inline-block;