Remove compatibility codes

common/tls/ech_stub.go

@@ -1,23 +0,0 @@
-//go:build !go1.24
-
-package tls
-
-import (
-	"context"
-	"crypto/tls"
-
-	"github.com/sagernet/sing-box/option"
-	E "github.com/sagernet/sing/common/exceptions"
-)
-
-func parseECHClientConfig(ctx context.Context, clientConfig ECHCapableConfig, options option.OutboundTLSOptions) (Config, error) {
-	return nil, E.New("ECH requires go1.24, please recompile your binary.")
-}
-
-func parseECHServerConfig(ctx context.Context, options option.InboundTLSOptions, tlsConfig *tls.Config, echKeyPath *string) error {
-	return E.New("ECH requires go1.24, please recompile your binary.")
-}
-
-func (c *STDServerConfig) setECHServerConfig(echKey []byte) error {
-	panic("unreachable")
-}