Updated reference to members importer template

- Have created a new v4 template, which is the same as the v3 template.
- Updating this reference now keeps it versioned, so that if we need to make changes just for v4 we can easily by just updating the asset

ghost/admin/app/components/modal-import-members.hbs

@@ -111,7 +111,7 @@
             </button>
             <a
                 class="gh-btn"
-                href="https://static.ghost.org/v3.0.0/files/member-import-template.csv"
+                href="https://static.ghost.org/v4.0.0/files/member-import-template.csv"
                 target="_blank"
             >
                 <span>Download sample CSV file</span>
@@ -141,7 +141,7 @@
         {{/if}}
 
         {{#if (eq this.state 'COMPLETE')}}
-            {{#if this.importResponse.errorCount}}                
+            {{#if this.importResponse.errorCount}}
                 <a href="{{this.importResponse.errorCsvUrl}}" download="{{this.importResponse.errorCsvName}}" class="gh-btn" data-test-button="restart-import-members">
                     <span>Download error file</span>
                 </a>