CLEANUP: mux-h2: remove two useless but misleading assignments

h2c->st0 was assigned to H2_CS_ERROR right after returning from
h2c_error(), which had already done it. It's useless and confusing,
let's remove this.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index f74ae32..afb3ad5 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -2237,7 +2237,6 @@
 
 			if ((int)hdr.len < 0 || (int)hdr.len > global.tune.bufsize) {
 				h2c_error(h2c, H2_ERR_FRAME_SIZE_ERROR);
-				h2c->st0 = H2_CS_ERROR;
 				if (!h2c->nb_streams) {
 					/* only log if no other stream can report the error */
 					sess_log(h2c->conn->owner);
@@ -2310,7 +2309,6 @@
 			 * this state MUST be treated as a connection error
 			 */
 			h2c_error(h2c, H2_ERR_PROTOCOL_ERROR);
-			h2c->st0 = H2_CS_ERROR;
 			if (!h2c->nb_streams) {
 				/* only log if no other stream can report the error */
 				sess_log(h2c->conn->owner);