chore: Add data-test tag for deauthenticate dropdown button

ui/core/app/templates/application.hbs

@@ -26,7 +26,10 @@
             @iconOnly={{true}}
             @icon="user-square-fill" as |dropdown|
           >
-            <dropdown.button {{on "click" (route-action "invalidateSession")}}>
+            <dropdown.button
+              data-test-deauthenticate
+              {{on "click" (route-action "invalidateSession")}}
+            >
               {{t 'actions.deauthenticate'}}
             </dropdown.button>
           </utilities.dropdown>

ui/core/tests/acceptance/authentication-test.js

@@ -164,7 +164,7 @@ module('Acceptance | authentication', function (hooks) {
     await fillIn('[name="password"]', 'test');
     await click('[type="submit"]');
     assert.ok(currentSession().isAuthenticated);
-    await click('.rose-button-header-dropdown');
+    await click('[data-test-deauthenticate]');
     assert.notOk(currentSession().isAuthenticated);
     assert.equal(currentURL(), authMethodAuthenticateURL);
   });