Prometheus: Add tooltip to explain possibility to use patterns in text and title fields in annotations (#30825)

* Add tip for using pattern

* Update public/app/plugins/datasource/prometheus/partials/annotations.editor.html

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>