Remove accidentally commented-out Group logic

Fixes: CNVS-35246

I introduced this bug when fixing CNVS-34740 by
commenting out some logic so I could see the search
input while working on the layout. The commented-out
logic was committed; this commit reinstates it.

Test plan:
- Go to [any course] > People > + Group Set
- Cancel out of the modal
- The search input for Search Groups should now only
  show if `groupsAreSearchable` is true

Change-Id: I63ddb564b44fc7f22cdda4388e1a2fff7cfa6543
Reviewed-on: https://gerrit.instructure.com/103321
Tested-by: Jenkins
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Product-Review: Colleen Palmer <colleen@instructure.com>
QA-Review: Chris Hart <chart@instructure.com>
QA-Review: Dan Sasaki

Author: Chris Hart

app/views/jst/groups/manage/groupCategory.handlebars

@@ -1,7 +1,7 @@
 <span class="accessibility-warning" tabindex="0"> Warning: for improved accessibility assigning students to groups, please use the Move To Dialog option found in the menu.</span>
 
 <div class="group-category-summary">
-  {{!#if groupsAreSearchable}}
+  {{#if groupsAreSearchable}}
     <div class="group-category-summary__search">
       <input
         type="text"
@@ -11,7 +11,7 @@
         role="search"
       >
     </div>
-  {{!/if}}
+  {{/if}}
   <div class="group-category-summary__detail" data-view="groupCategoryDetail"></div>
 </div>