audio/mumble-server: update to 1.5.517

Upstream renamed murmur to mumble-server.

Changelogs:
https://github.com/mumble-voip/mumble/releases/tag/v1.5.517
https://github.com/mumble-voip/mumble/releases/tag/v1.4.287
https://github.com/mumble-voip/mumble/releases/tag/v1.4.274
https://github.com/mumble-voip/mumble/releases/tag/v1.4.230

PR: 261395
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D41048