multimedia/libopenshot: Update 0.6.0 => 0.7.0

The audio input and output issues have been resolved.

News:
https://www.openshot.org/blog/2026/04/06/openshot-351-faster-performance-smoother-editing-better-previews/

Changelog:
https://github.com/OpenShot/libopenshot/releases/tag/v0.7.0

PR: 294379
Sponsored by: UNIS Labs
MFH: 2026Q2

(cherry picked from commit 8d13862a00aba104336be5fe2af369018f5dd685)