multimedia/gmp-api: update to 92

• Only gmp-storage.h is under Apache-2.0 license
• Simplify description as the API hasn't really changed for years

Changes: https://github.com/mozilla/gmp-api/compare/e393575...Firefox92
Reported by: portscout

(cherry picked from commit c04c764498b8da55bb8ad3628ec6c9c25901baf8)