MINOR: connection: Remove the multiplexer protocol PROTO_MODE_HTX

Since the legacy HTTP mode is disabled and no multiplexer relies on it anymore,
there is no reason to have 2 multiplexer protocols for the HTTP. So the protocol
PROTO_MODE_HTX was removed and all HTTP multiplexers use now PROTO_MODE_HTTP.
diff --git a/include/proto/connection.h b/include/proto/connection.h
index 02f3234..9b4ac51 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -929,10 +929,6 @@
 			mode = "TCP";
 		else if (item->mode == PROTO_MODE_HTTP)
 			mode = "HTTP";
-		else if (item->mode == PROTO_MODE_HTX)
-			mode = "HTX";
-		else if (item->mode == (PROTO_MODE_HTTP | PROTO_MODE_HTX))
-			mode = "HTTP|HTX";
 		else
 			mode = "NONE";
 
@@ -1043,7 +1039,7 @@
 		int mode;
 
 		if (bind_conf->frontend->mode == PR_MODE_HTTP)
-			mode = ((bind_conf->frontend->options2 & PR_O2_USE_HTX) ? PROTO_MODE_HTX : PROTO_MODE_HTTP);
+			mode = PROTO_MODE_HTTP;
 		else
 			mode = PROTO_MODE_TCP;
 
@@ -1081,7 +1077,7 @@
 		int mode;
 
 		if (prx->mode == PR_MODE_HTTP)
-			mode = ((prx->options2 & PR_O2_USE_HTX) ? PROTO_MODE_HTX : PROTO_MODE_HTTP);
+			mode = PROTO_MODE_HTTP;
 		else
 			mode = PROTO_MODE_TCP;
 
diff --git a/include/types/connection.h b/include/types/connection.h
index cc2fb17..6609f8b 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -471,8 +471,7 @@
 	PROTO_MODE_NONE = 0,
 	PROTO_MODE_TCP  = 1 << 0, // must not be changed!
 	PROTO_MODE_HTTP = 1 << 1, // must not be changed!
-	PROTO_MODE_HTX  = 1 << 2, // must not be changed!
-	PROTO_MODE_ANY  = PROTO_MODE_TCP | PROTO_MODE_HTTP, // note: HTX is experimental and must not appear here
+	PROTO_MODE_ANY  = PROTO_MODE_TCP | PROTO_MODE_HTTP,
 };
 
 enum proto_proxy_side {
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 1101470..9bfe874 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -3585,10 +3585,6 @@
 			int mode = (1 << (curproxy->mode == PR_MODE_HTTP));
 			const struct mux_proto_list *mux_ent;
 
-			/* Special case for HTX because legacy HTTP still exists */
-			if (mode == PROTO_MODE_HTTP && (curproxy->options2 & PR_O2_USE_HTX))
-				mode = PROTO_MODE_HTX;
-
 			if (!bind_conf->mux_proto)
 				continue;
 
@@ -3614,10 +3610,6 @@
 			int mode = (1 << (curproxy->mode == PR_MODE_HTTP));
 			const struct mux_proto_list *mux_ent;
 
-			/* Special case for HTX because legacy HTTP still exists */
-			if (mode == PROTO_MODE_HTTP && (curproxy->options2 & PR_O2_USE_HTX))
-				mode = PROTO_MODE_HTX;
-
 			if (!newsrv->mux_proto)
 				continue;
 
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 009afb0..099cd22 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -479,7 +479,7 @@
 			if (h1c->wait_event.events)
 				conn->xprt->unsubscribe(conn, conn->xprt_ctx,
 				    h1c->wait_event.events, &h1c->wait_event);
-			if (conn_upgrade_mux_fe(conn, NULL, &h1c->ibuf, ist("h2"), PROTO_MODE_HTX) != -1) {
+			if (conn_upgrade_mux_fe(conn, NULL, &h1c->ibuf, ist("h2"), PROTO_MODE_HTTP) != -1) {
 				/* connection successfully upgraded to H2, this
 				 * mux was already released */
 				return;
@@ -2533,7 +2533,7 @@
 
 /* this mux registers default HTX proto */
 static struct mux_proto_list mux_proto_htx =
-{ .token = IST(""), .mode = PROTO_MODE_HTX, .side = PROTO_SIDE_BOTH, .mux = &mux_h1_ops };
+{ .token = IST(""), .mode = PROTO_MODE_HTTP, .side = PROTO_SIDE_BOTH, .mux = &mux_h1_ops };
 
 INITCALL1(STG_REGISTER, register_mux_proto, &mux_proto_htx);
 
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 271d19a..10bad14 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -5163,7 +5163,7 @@
 };
 
 static struct mux_proto_list mux_proto_h2 =
-	{ .token = IST("h2"), .mode = PROTO_MODE_HTX, .side = PROTO_SIDE_BOTH, .mux = &h2_ops };
+	{ .token = IST("h2"), .mode = PROTO_MODE_HTTP, .side = PROTO_SIDE_BOTH, .mux = &h2_ops };
 
 INITCALL1(STG_REGISTER, register_mux_proto, &mux_proto_h2);
 
diff --git a/src/proxy.c b/src/proxy.c
index 57efc38..518ee35 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -1477,7 +1477,7 @@
 				if (s->si[0].wait_event.events)
 					conn->mux->unsubscribe(cs, s->si[0].wait_event.events,
 					    &s->si[0].wait_event);
-				if (conn_upgrade_mux_fe(conn, cs, &s->req.buf, ist(""), PROTO_MODE_HTX)  == -1)
+				if (conn_upgrade_mux_fe(conn, cs, &s->req.buf, ist(""), PROTO_MODE_HTTP)  == -1)
 					return 0;
 				s->flags |= SF_HTX;
 			}