opus_header: fix channel mapping family 1 parsing

Fixes #27808 (closed)

The existing code was lumping channel family mapping 1 into the else catch all that deals with parsing the ambisonic decoding matrix (channel family 3) and failing, when in fact:

[channel mapping family 2] uses the same channel mapping table format used by channel mapping family 1. [1]

[1] https://www.rfc-editor.org/rfc/rfc8486.html#section-3.1