Call Release in SimulcastEncoderAdapter destructor if inited.

This check should be superflous once
https://webrtc-review.git.corp.google.com/c/src/+/465582 has landed,
but just to be safe make sure we always call Release() in the destructor
if it hasn't already been called.

Bug: chromium:504620824
Change-Id: I70323b1a71fd9830f0d7af62ebeced05dd833d54
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/465600
Auto-Submit: Erik Språng <sprang@webrtc.org>
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47496}