Remove btn-inverted-secondary since it is not referenced anywhere

app/assets/stylesheets/framework/buttons.scss

@@ -174,12 +174,6 @@
   }
 }
 
-.btn-inverted {
-  &-secondary {
-    @include btn-outline($white, $blue-500, $blue-500, $blue-100, $blue-700, $blue-500, $blue-200, $blue-600, $blue-800);
-  }
-}
-
 .btn-blank {
   padding: 0;
   background: transparent;