release-notes: updates for the 20240730 releases

[marmijo]

NOTE: there are syntax errors in the initial push to test #934

EDIT: Syntax errors have been corrected

[marmijo]

Nice! Great job on #934 @aaradhak

Error loading YAML file: mapping values are not allowed here
  in "release-notes/next.yml", line 3, column 11
Validating release-notes/stable.yml...
Validating release-notes/testing.yml...
Error: 'issues' key for release 40.20240[7](https://github.com/coreos/fedora-coreos-streams/actions/runs/10308721273/job/28536791362?pr=936#step:3:8)28.2.1 should contain a list.
Traceback (most recent call last):
  File "/home/runner/work/fedora-coreos-streams/fedora-coreos-streams/ci/check-release-notes.py", line [8](https://github.com/coreos/fedora-coreos-streams/actions/runs/10308721273/job/28536791362?pr=936#step:3:9)4, in <module>
    main()
  File "/home/runner/work/fedora-coreos-streams/fedora-coreos-streams/ci/check-release-notes.py", line 75, in main
    if not validate_release_notes_structure(data):
  File "/home/runner/work/fedora-coreos-streams/fedora-coreos-streams/ci/check-release-notes.py", line 43, in validate_release_notes_structure
    for issue in content.get('issues', []):
TypeError: 'NoneType' object is not iterable

due to no colon here:

fedora-coreos-streams/release-notes/next.yml

Lines 2 to 3 in fe6b4a1

	40.20240728.1.1
	issues: []

and no list (brackets) here:

fedora-coreos-streams/release-notes/testing.yml

Lines 2 to 3 in fe6b4a1

	40.20240728.2.1:
	issues:

[marmijo]

closing in favor of #946