FIX: Ensure the like button always has a title, for accessibility (#6525)

The like button previously didn't have a title for anonymous users,
because the `canToggleLike` flag wasn't set, but the `liked` flag wasn't
set either. This made the button inaccessible to blind users.

test/javascripts/widgets/post-test.js.es6

@@ -206,6 +206,12 @@ widgetTest("anon liking", {
     assert.ok(!!this.$(".actions button.like").length);
     assert.ok(this.$(".actions button.like-count").length === 0);
 
+    assert.equal(
+      this.$("button.like").attr("title"),
+      I18n.t("post.controls.like"),
+      `shows the right button title for anonymous users`
+    );
+
     await click(".actions button.like");
     assert.ok(this.loginShown);
   }