fix: disable psiphon when building with go1.19 (#871)

Part of https://github.com/ooni/probe/issues/2211.

See also https://github.com/ooni/probe/issues/2222, which
describes the issue we have with psiphon and go1.19.

internal/tunnel/psiphon_go119.go

@@ -0,0 +1,19 @@
+//go:build go1.19
+
+package tunnel
+
+//
+// Psiphon not working with go1.19: TODO(https://github.com/ooni/probe/issues/2222)
+//
+
+import (
+	"context"
+	"errors"
+)
+
+// psiphonStart starts the psiphon tunnel.
+func psiphonStart(ctx context.Context, config *Config) (Tunnel, DebugInfo, error) {
+	return nil, DebugInfo{}, errors.New(
+		"psiphon is disabled when building with go1.19: see https://github.com/ooni/probe/issues/2222 for more information",
+	)
+}