chore: Remove unnecessary task when installing modules on Alpine Linux

[alessfg]

Proposed changes

Installing certain NGINX modules on Alpine Linux 3.17 no longer requires installing nginx-plus-module-ndk as a separate step. This PR also includes a minor bug fix hat should have been part of the original PR removing support for RHEL 7 based distributions involving EPEL 7 repos being no longer available.

Checklist

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• I have read the contributing guidelines.
• I have signed the F5 Contributor License Agreement (CLA).
• If applicable, I have added Molecule tests that prove my fix is effective or that my feature works.
• If applicable, I have checked that any relevant Molecule tests pass after adding my changes.
• I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md).