[9.1] (backport #17924) Move logstash release information to .ci (#17942)

* Move logstash release information to `.ci` (#17924)

Consumers of this information are already cloning the `.ci` repo. They
subsequently curl logstash for this information. Moving to `.ci` reduces steps
and removes the need to track this across information in active streams of
logstash.

(cherry picked from commit 95a0466)

# Conflicts:
#	ci/logstash_releases.json

* Remove logstash_releases.json

---------

Co-authored-by: Cas Donoghue <[email protected]>

Author: mergify[bot]