Feature Request: Add `--enable-release-immutability` flag to `gh repo edit`

### Clarification
Currently, the `gh repo edit` command allows users to enable or disable various repository features like issues, wikis, and projects. However, it lacks a flag to toggle the "Release Immutability" setting (`Settings > General > Releases > Enable release immutability`).

### Proposed Solution
Add a flag such as `--enable-release-immutability` to `gh repo edit`. This would allow organization administrators and automation scripts to enforce release immutability across an estate of repositories without needing to manually click through the web UI for each repository.

### Additional Context
Release immutability is a critical software supply chain security feature. Being able to automate its enablement alongside other repository settings would greatly improve the security posture of bulk-managed repositories.

Start at the existing `gh repo edit` command and its repository-settings update path, then inspect how current feature-toggle flags map to the GitHub API. Confirm the release immutability setting is available to this command and determine the expected flag behavior. Done means the new flag can enable release immutability for a repository, with coverage alongside the existing edit settings.

Written by the indexing model from the issue text.