Fix error message about QA template

GitHub complains:
> title must be of type String and cannot be empty. Learn more about this error.

Well then… as we don't want to provide a default title (see https://github.com/PrivateBin/PrivateBin/pull/1155) let's remove it.

.github/DISCUSSION_TEMPLATE/q-a.yml

@@ -1,4 +1,3 @@
-title: ""
 labels: ["question/support"]
 body:
   - type: markdown