fix: Simplify v15 CHANGELOG.md entry

What does this MR do?

Simplifies CHANGELOG.md entry which had enough complexity to break the scripts/release-utils.sh script. We could alternatively escape all the necessary characters but TBH it feels overly complex to bother so I went with "simpler changelog entry".

See failure https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/jobs/2999433914

Follow-up action: Add changelog JSON validation to avoid pipeline breakages.

Testing

Before

❯ git rev-parse HEAD
8bac8eda06634222a815010a6381ddc689ff2953
❯ GITLAB_API_TOKEN=GITLAB_API_TOKEN ./scripts/release.sh


######### Initializing environment #########
parse error: Invalid literal at line 1, column 1000
Aborting, extracted release data type '' is not a JSON object. Release data: {"tag_name":"v15.0.0","description":" ##### Changes\n - Mark `scan` and `scan.analyzer` as required (!102)\n- Mark `vulnerabilities[].id` as required (!108)\n- Mark `remediations[].fixes[].id` as required (!118)\n- Mark properties in `dependency_files[].dependency` as required (!114):\n  - `version`\n  - `package`\n  - `package.name`\n- Remove `vulnerabilities[].category` (!109)\n- Remove `vulnerabilities[].confidence` (!109)\n- Remove `vulnerabilities[].cve` (!108)\n- Remove `remediations[].fixes[].cve` (!118)\n- Remove `vulnerabilities[].message` (!109)\n- Remove `vulnerabilities[].scanner` (!109)\n- (DAST) Remove `vulnerabilities[].discovered_at` (!109)\n- Enforce maximum length limits for the following fields:\n  - `vulnerabilities[].description` (!110)\n  - `vulnerabilities[].name` (!110)\n  - `vulnerabilities[].solution` (!125)\n- Add `$id` property to all schemas (!111)\n- Fix pattern for `scan.start_time` and `scan.end_time` properties (!112)\n- Replace invalid use of `"format": "uri"` with `"pattern": "^https?://.+"` (!122) \n\n ##### Secure Report Format Schemas\n - https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/raw/v15.0.0/dist/container-scanning-report-format.json\n - https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/raw/v15.0.0/dist/dast-report-format.json\n - https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/raw/v15.0.0/dist/sast-report-format.json\n - https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/raw/v15.0.0/dist/coverage-fuzzing-report-format.json\n - https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/raw/v15.0.0/dist/dependency-scanning-report-format.json\n - https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/raw/v15.0.0/dist/secret-detection-report-format.json\n"}%

After

❯ git checkout remotes/origin/theoretick-master-patch-21425
HEAD is now at 68c77e4 fix: Simplify v15 CHANGELOG.md entry
❯ GITLAB_API_TOKEN=GITLAB_API_TOKEN ./scripts/release.sh


######### Initializing environment #########


######### Detected Secure Report Format v15.0.0, verifying not already released #########

Aborting, CI Project ID has not been supplied to verify_version_not_released

What are the relevant issue numbers?

Relates to !100 (comment 1093253264)

Checklist

• Ensure changes can be built upon without requiring a breaking change, see Building for Extensibility.
• Review and add/update tests for this feature/bug.
• Add an entry to the CHANGELOG if required, with the appropriate version. See Classifying Changes.
• Assign the MR to the appropriate person/people for review.