fix ms2 version for opus

[linphone] / mediastreamer2

diff --git a/mediastreamer2 b/mediastreamer2
index 2b43ce538299df8d9bc9d8f37de5f74a05342792..ef59e93709972e8e7ed1a4b642f0c113b575916f 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit 2b43ce538299df8d9bc9d8f37de5f74a05342792
+Subproject commit ef59e93709972e8e7ed1a4b642f0c113b575916f