I'm seeing this error in the logs:
> invalid additional property: emoji [json-pointer:/blocks/0/text]
It looks like the 'emoji' argument is not supported when type: mrkdwn.
This PR removes that property in the same place that the change
to mrkdwn was made - see [this
PR](https://github.com/grafana/oncall/pull/646).
(cherry picked from commit 6ef687061c)