chore: bump marshmallow from 3.26.1 to 3.26.2 in /services/admin-backend

Bumps [marshmallow](https://github.com/marshmallow-code/marshmallow) from 3.26.1 to 3.26.2.
- [Changelog](https://github.com/marshmallow-code/marshmallow/blob/3.26.2/CHANGELOG.rst)
- [Commits](marshmallow-code/marshmallow@3.26.1...3.26.2)

---
updated-dependencies:
- dependency-name: marshmallow
  dependency-version: 3.26.2
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]