remove code

src/client/styles/scss/theme/_apply-colors.scss

@@ -175,18 +175,6 @@ $link-hover-color: $color-link-hover;
   }
 }
 
-/*
- * Crowi sidebar
- */
-.crowi-sidebar {
-  background-color: darken($bgcolor-global, 4%);
-  border-left: solid 1px $border-color;
-
-  .system-version {
-    background-color: darken($bgcolor-global, 4%);
-  }
-}
-
 /*
  * GROWI wiki
  */