chore: fix typo in service key name

[assyrus-favolo]

---

title: "Use correct name for hostname key in documentation"

Description

There was a typo in the documentation for the key hostname, written as hostnames.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Documentation update
• Other (please describe):

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Additional Context / Screenshots (if appropriate)

Reference: https://docs.docker.com/reference/compose-file/services/#hostname