Fix `lib/github_advisory_sync.rb` script to indent `patched_versions:` and `related:/url:` 2 spaces to the right

[jasnow]

Fix lib/github_advisory_sync.rb script to indent patched_versions: and related:/url: 2 spaces to the right.

Example:

BEFORE

patched_versions:
- ">= 3.0.1"
related:
  url:
  - https://github.com/autolab/Autolab/security/advisories/GHSA-v46j-h43h-rwrm

AFTER

patched_versions:
  - ">= 3.0.1"
related:
  url:
    - https://github.com/autolab/Autolab/security/advisories/GHSA-v46j-h43h-rwrm