* pushover: Customise OK notification priorities

* Apply suggestions from code review

* Fix build failure

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/services/alerting/notifiers/pushover.go

Co-authored-by: Sofia Papagiannaki <papagian@users.noreply.github.com>

* Update docs

* Apply suggestions from code review

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
Co-authored-by: Sofia Papagiannaki <papagian@users.noreply.github.com>
Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>