audio/strawberry: Add missing dep for Radios

devel/gstreamer1-plugins-soup is required for the Radios (HTTP/HTTPS
streaming) feature to function.

PR: 288099
Reported by: Thomas Dreibholz <thomas.dreibholz@gmail.com>
MFH: 2025Q4

(cherry picked from commit b474e448fe246c014eb1154a949b3093826402a9)