Add missing fields for suppressor alarm

[kdnakt]

Issue #, if available:

Description of changes:

actionsSuppressedBy and actionsSuppressedReason are in the example json file.

example-cloudwatch-alarm-composite-with-suppressor-alarm.json
is from this document.

By submitting this pull request

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I confirm that I've made a best effort attempt to update all relevant documentation.

[calavera]

Thanks!