Move callout render check to computed

Moving a render check to a computed prop
so that we can be more efficient.

app/assets/javascripts/jobs/components/job_app.vue

@@ -130,6 +130,10 @@ export default {
 
       return title;
     },
+
+    shouldRenderHeaderCallout() {
+      return this.shouldRenderCalloutMessage && !this.hasUnmetPrerequisitesFailure;
+    },
   },
   watch: {
     // Once the job log is loaded,
@@ -239,7 +243,7 @@ export default {
             />
           </div>
 
-          <callout v-if="shouldRenderCalloutMessage && !hasUnmetPrerequisitesFailure">
+          <callout v-if="shouldRenderHeaderCallout">
             <div v-html="job.callout_message"></div>
           </callout>
         </header>