(from AES) CHANGELOG: Fix up
(from AES) CHANGELOG: Fix up

- Add a missing "Ambassador Edge Stack only" heading
- Consistent capitalization: "Bugfix", not "BugFix"
- All of the AES-only changes in 1.9.0 were listed twice because of a bad
  merge
- Two devportal changes in 1.9.0 were listed in the OSS section instead of
  the AES section.
- The 1.3.0 release said `diagnostics.enable` instead of
  `diagnostics.enabled`.

datawire/ambassador,datawire/ambassador,datawire/ambassador,datawire/ambassador,datawire/ambassador