docs: update docs for allowed propagating apis flag

[vasudev-bongale]

Summary

A new flag --allowed-propagating-apis was introduced in #633. I am updating the reference docs to describe how the user can use this flag.

Fixes #649

I have:

• Run make reviewable to ensure this PR is ready for review.

Testing

Rendered the markdown locally and ran make test

Special notes for your reviewer

• api-resources doc has been updated to suggest that if a namespace is selected, the default behavior of ALL resource propagation can be controlled with this flag.