chore!: Remove support for RHEL 7 based distributions

[alessfg]

Proposed changes

Remove support for RHEL 7 based distributions (RHEL/CentOS/Oracle Linux 7). CentOS 7 has reached EoL, RHEL 7 has reached EoM, and Oracle Linux 7 will reach EoL shortly. These distributions will not be supported by new NGINX releases moving forward. If you are still using one of these distributions, please consider upgrading. If you still want to use this role for the time being, please use the previous release (0.24.3). Do note that you will only be able to use NGINX versions released as of the date of the aforementioned release (July 11, 2024).

Checklist

Before creating a PR, run through this checklist and mark each as complete:

• I have read the CONTRIBUTING document.
• I have added Molecule tests that prove my fix is effective or that my feature works.
• 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).