Recent merging of the liaison-loading code in list-changes makes
most list-changes job fail due to error in YAML loading code.
Beyond that YAML loading issue, the code assumes getting a dictionary
with team names as keys and an array of liaisons dictionary as values.
Fix the release_liaisons.yaml and schema to match.
Change-Id: I94fa41862d37aaf0535d64afd00b2bd55bb4649a
Now that the release liaison info lives in data/release_liaisons.yaml,
we don't need to pull from the wiki. This patch also adds a schema
to verify the release_liaions.yaml is formatted correctly.
Story: 2005702
Task: 33639
Task: 33733
Change-Id: Ic4de16c26bb1a4fb878b86d2bd9c59bf5f54d11d