jira: config: Rename a local config field

The field that was called project_id_or_key is now called simply project_key,
it is actually better to know what is written there, even though it looks like
it doesn't really matter from the JIRA API perspective. And it's shorter.

Change-Id: b6b8458828
wip

Change-Id: 9185eab20e
Story-Id: SF-6