contrib: rav1e: update to rav1e 0.6.6
From https://github.com/xiph/rav1e/releases/tag/v0.6.6:
* Sync the assembly with dav1d
* Additional improvements and cleanups
* Overall speed-up typically 5.2%Edited by Tristan Matthews
From https://github.com/xiph/rav1e/releases/tag/v0.6.6:
* Sync the assembly with dav1d
* Additional improvements and cleanups
* Overall speed-up typically 5.2%VideoLAN code repository instance