Bump alpine from 3.20.2 to 3.20.3 in /docker

Bumps alpine from 3.20.2 to 3.20.3.

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>