FIX: Show parent and subcategories for 2nd level categories (#8579)

The maximum level used to be one, which meant that a category could be
either a parent or a child. If it was a parent, the subcategories were
shown; if it was a child then the parent selector was shown.

With multiple levels of nesting, a category can be both a parent and a
child.

app/assets/javascripts/discourse/templates/components/edit-category-general.hbs

@@ -10,21 +10,23 @@
 
   {{#if canSelectParentCategory}}
     <section class='field'>
-      {{#if subCategories}}
-        <label>{{i18n 'categories.subcategories'}}</label>
-        {{#each subCategories as |s|}}
-          {{category-badge s hideParent="true"}}
-        {{/each}}
-      {{else}}
-        <label>{{i18n 'category.parent'}}</label>
-        {{category-chooser
-          none="category.none"
-          value=category.parent_category_id
-          excludeCategoryId=category.id
-          categories=parentCategories
-          allowSubCategories=true
-          allowUncategorized=false}}
-      {{/if}}
+      <label>{{i18n 'category.parent'}}</label>
+      {{category-chooser
+        none="category.none"
+        value=category.parent_category_id
+        excludeCategoryId=category.id
+        categories=parentCategories
+        allowSubCategories=true
+        allowUncategorized=false}}
+    </section>
+  {{/if}}
+
+  {{#if subCategories}}
+    <section class='field'>
+      <label>{{i18n 'categories.subcategories'}}</label>
+      {{#each subCategories as |s|}}
+        {{category-badge s hideParent="true"}}
+      {{/each}}
     </section>
   {{/if}}
 

app/assets/stylesheets/desktop/modal.scss

@@ -58,6 +58,12 @@
     height: 420px;
   }
 
+  .edit-category-tab-general {
+    .category-chooser {
+      width: 434px;
+    }
+  }
+
   .disable_info_wrap {
     .cannot_delete_reason {
       top: -100px;