ui: fix problem edit&create category display

packages/ui-default/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@hydrooj/ui-default",
-  "version": "4.8.33",
+  "version": "4.8.34",
   "author": "undefined <i@undefined.moe>",
   "license": "AGPL-3.0",
   "main": "hydro.js",

packages/ui-default/pages/problem_main.page.styl

@@ -31,7 +31,7 @@
       border-left: 1px solid $table-border-color
 
 
-  .widget--category-filter
+.widget--category-filter
   &__category
     margin-bottom: rem(6px)
 
@@ -91,7 +91,7 @@
         color: #FFF
         background: $secondary-color
 
-  .drop-target-attached-right .widget--category-filter__drop
+.drop-target-attached-right .widget--category-filter__drop
   margin-right: 0
   margin-left: rem(10px)