drop cfg 'sdp audio fmtp-extra'

There is considerable code complexity in place for this ancient hack.

It dates back to 5ea1bc77a3947f541d576f95e7ecc7249fc65b9b
"
mgcp: Allow to freely control the a=fmtp line for experiments

In case of AMR one can specify the available codecs out-of-band. Allow
to configure this line statically in the configuration file.
"

Looking in mgcp_test.c output, the fmtp-extra tests do not even make
sense: they result in fmtp for pt=126 being added, even though there is
no payload type 126 listed in the SDP...

Related: OS#6313
Change-Id: Icee0cd1f5a751fa760d5a9deca29089e78e7eb93
diff --git a/TODO-RELEASE b/TODO-RELEASE
index 964ffe1..ea29b6a 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -38,3 +38,4 @@
 libosmo-mgcp-client	deprecate public API	New code should no longer use codecs[], instead use ptmap[].codec. There
 						is backwards compat code that moves codecs[] entries, if any, over to
 						ptmap[], so callers may migrate at own leisure.
+osmo-mgw		remove cfg		Remove VTY config item 'sdp audio fmtp-extra' (see OS#6313)