Add canLoad checks to AVVideoCaptureSource::facingModeFitnessScoreAdjustment implementation
<rdar://107677782>
Pull request: https://github.com/WebKit/WebKit/pull/12434
Committed 262676@main (4adf11746cc7): <https://commits.webkit.org/262676@main> Reviewed commits have been landed. Closing PR #12434 and removing active labels.