fix(sms): Use the same graphic on /sms/sent as /sms (#5601) r=@ryanfeeley

Removed the sms-sent* images, they are no longer used.

fixes #5589

app/scripts/templates/sms_sent.mustache

@@ -13,7 +13,7 @@
       {{/isResend}}
     <div class="error"></div>
 
-    <div class="graphic graphic-sms-sent">{{#t}}Success{{/t}}</div>
+    <div class="graphic graphic-connect-another-device">{{#t}}Success{{/t}}</div>
 
     <p id="sms-sent-to">
       {{#t}}Install Firefox on your smartphone and sign in to complete set-up{{/t}}

app/styles/modules/_graphic.scss

@@ -65,11 +65,4 @@
   @include respond-to('small') {
     height: 100px;
   }
-}
-
-.graphic-sms-sent {
-  @include hidpi-background-image('sms-sent', 310px 87px);
-  height: 87px;
-  margin: 35px auto;
-  width: 310px;
-}
+}