Fix issue where codec fallback skips first codec in list.

Before this CL, `ApplyEncoderSwitch` implicitly assumed that
`send_codec()` is the first codec in `negotiated_codecs_`, but this is a
very outdated assumption that assumes that the only way to pick a codec
is with the SDP preference order (e.g. `SetCodecPreferences()` or SDP
munging).

But it has long been the case that `SetParameters()` can pick another
codec. This CL updates the logic to remove the `send_codec()` where
ever it is located, resulting in the next codec to test being the first
one in the list should the current one not be the first one already.

Bug: chromium:556170878
Change-Id: I7c8f50537ef52cae3af2c0d460096a4b97045703
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/498561
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48477}