Fix temporal index overflow in RtpPayloadParams

H264ToGeneric() and Vp8ToGeneric() accepted temporal indices up to 7 but
sized the decode target indications for kMaxTemporalStreams (4) temporal
layers, so indices 4-7 hit a DCHECK or wrote past the end of the vector.
Reject them like larger indices.

Fixed: webrtc:566486041
Change-Id: Ifdb3f6554a6aabbcec79f0f866aa5ced578b655a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/505682
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48755}