MINOR: connection: unconst mux's get_fist_cs() callback function
This change is mandatory for next commits.
diff --git a/src/mux_pt.c b/src/mux_pt.c
index 97b3b83..0c36c79 100644
--- a/src/mux_pt.c
+++ b/src/mux_pt.c
@@ -399,7 +399,7 @@
/* Retrieves a valid conn_stream from this connection, or returns NULL. For
* this mux, it's easy as we can only store a single conn_stream.
*/
-static const struct conn_stream *mux_pt_get_first_cs(const struct connection *conn)
+static struct conn_stream *mux_pt_get_first_cs(const struct connection *conn)
{
struct mux_pt_ctx *ctx = conn->ctx;