Clean up `read_package_policy_rule` feature flag

What does this MR do and why?

The read_package_policy_rule feature flag was introduced in !90963 (merged) and the feature flag will be rolled out in #366711 (closed).

This MR cleans up the read_package_policy_rule feature flag.

🛠 with ❤ at Siemens

/cc @bufferoverflow

How to set up and validate locally

see !90963 (merged)

MR acceptance checklist

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