Integrate RTCRtpEncodingParameters maxFramerate test into main webrtc folder (#43173)

per https://github.com/w3c/webrtc-pc/pull/2785
diff --git a/webrtc-extensions/RTCRtpParameters-maxFramerate.html b/webrtc/RTCRtpParameters-maxFramerate.html
similarity index 100%
rename from webrtc-extensions/RTCRtpParameters-maxFramerate.html
rename to webrtc/RTCRtpParameters-maxFramerate.html