github: azure: Update our GitHub template to note for CI

While the general policy of not taking changes to the project via pull
requests directly on GitHub has not changed, it can be useful to submit
a PR there in order to trigger a CI run on Azure.  These are run
automatically and the results are populated back to GitHub.  Add a note
to the template to reflect this.

Signed-off-by: Tom Rini <trini@konsulko.com>