don't re-implement osmo_talloc_replace_string()

osmo_talloc_replace_string() was introducd into libosmocore in 2014, see
commit f3c7e85d05f7b2b7bf093162b776f71b2bc6420d

There's no reason for us to re-implement this as bsc_replace_string
here.

Change-Id: I6d2fcaabbc74730f6f491a2b2d5c784ccafc6602
diff --git a/openbsc/tests/mgcp/mgcp_test.c b/openbsc/tests/mgcp/mgcp_test.c
index b2d237e..43a453a 100644
--- a/openbsc/tests/mgcp/mgcp_test.c
+++ b/openbsc/tests/mgcp/mgcp_test.c
@@ -532,7 +532,7 @@
 		last_endpoint = -1;
 		dummy_packets = 0;
 
-		bsc_replace_string(cfg, &cfg->trunk.audio_fmtp_extra, t->extra_fmtp);
+		osmo_talloc_replace_string(cfg, &cfg->trunk.audio_fmtp_extra, t->extra_fmtp);
 
 		inp = create_msg(t->req);
 		msg = mgcp_handle_message(cfg, inp);