Update srtp to 2.0.6.

This contains some important optimisations for CTR mode.

go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/pion/rtcp v1.2.9
 	github.com/pion/rtp v1.7.13
 	github.com/pion/sdp/v3 v3.0.4
+	github.com/pion/srtp/v2 v2.0.6 // indirect
 	github.com/pion/turn/v2 v2.0.8
 	github.com/pion/webrtc/v3 v3.1.34
 	golang.org/x/crypto v0.0.0-20220411220226-7b82a4e95df4

go.sum

@@ -81,8 +81,9 @@ github.com/pion/sctp v1.8.2 h1:yBBCIrUMJ4yFICL3RIvR4eh/H2BTTvlligmSTy+3kiA=
 github.com/pion/sctp v1.8.2/go.mod h1:xFe9cLMZ5Vj6eOzpyiKjT9SwGM4KpK/8Jbw5//jc+0s=
 github.com/pion/sdp/v3 v3.0.4 h1:2Kf+dgrzJflNCSw3TV5v2VLeI0s/qkzy2r5jlR0wzf8=
 github.com/pion/sdp/v3 v3.0.4/go.mod h1:bNiSknmJE0HYBprTHXKPQ3+JjacTv5uap92ueJZKsRk=
-github.com/pion/srtp/v2 v2.0.5 h1:ks3wcTvIUE/GHndO3FAvROQ9opy0uLELpwHJaQ1yqhQ=
 github.com/pion/srtp/v2 v2.0.5/go.mod h1:8k6AJlal740mrZ6WYxc4Dg6qDqqhxoRG2GSjlUhDF0A=
+github.com/pion/srtp/v2 v2.0.6 h1:sTS0ptsREtS+XJIagwPYMCFQPKE7TpYTz8BDTXcn0y8=
+github.com/pion/srtp/v2 v2.0.6/go.mod h1:5TtM9yw6lsH0ppNCehB/EjEUli7VkUgKSPJqWVqbhQ4=
 github.com/pion/stun v0.3.5 h1:uLUCBCkQby4S1cf6CGuR9QrVOKcvUwFeemaC865QHDg=
 github.com/pion/stun v0.3.5/go.mod h1:gDMim+47EeEtfWogA37n6qXZS88L5V6LqFcf+DZA2UA=
 github.com/pion/transport v0.10.1/go.mod h1:PBis1stIILMiis0PewDw91WJeLJkyIMcEk+DwKOzf4A=