🐛 fix jumping "Invite User" button when modal is opened

closes TryGhost/Ghost#7890
- moved the modal outside of the `<header>` tag to avoid triggering unexpected flexbox justification

ghost/admin/app/templates/team/index.hbs

@@ -6,14 +6,14 @@
             <section class="view-actions">
                 <button class="btn btn-green" {{action "toggleInviteUserModal"}} >Invite People</button>
             </section>
+        {{/unless}}
+    </header>
 
     {{#if showInviteUserModal}}
         {{gh-fullscreen-modal "invite-new-user"
                               close=(action "toggleInviteUserModal")
                               modifier="action"}}
     {{/if}}
-        {{/unless}}
-    </header>
 
     {{#gh-infinite-scroll
         fetch="loadNextPage"