audio/gtultra: Update to 1.5.5
Changes:
https://github.com/jpage8580/GTUltra/releases/tag/V1.5.4.2
https://github.com/jpage8580/GTUltra/releases/tag/V1.5.4.3
https://github.com/jpage8580/GTUltra/releases/tag/V1.5.4.4
https://github.com/jpage8580/GTUltra/releases/tag/V1.5.5
Reported by: portscout
Approved by: tcberner (mentor, implicit)