[Release|CI/CD] Fix audiences changelog template (#6444)

This PR addresses an issue mentioned
[here](https://github.com/paritytech/polkadot-sdk/issues/6424#issuecomment-2467042441).
The problem was that when the prdoc file has two audiences, but only one
description like in
[prdoc_5660](https://github.com/paritytech/polkadot-sdk/blob/master/prdoc/1.16.0/pr_5660.prdoc)
it was ignored by the template.