build(deps-dev): bump eslint-config-etherpad in /src (#5791)

Bumps [eslint-config-etherpad](https://github.com/ether/eslint-config-etherpad) from 3.0.13 to 3.0.15.
- [Commits](ether/eslint-config-etherpad@v3.0.13...v3.0.15)

---
updated-dependencies:
- dependency-name: eslint-config-etherpad
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]