refactor: only use shaping dialer for ndt7 and dash (#754)

See https://github.com/ooni/probe/issues/2112 for context.

While there, run `go fix -fix buildtag ./...`

internal/netxlite/shaping_otherwise_test.go

@@ -0,0 +1,17 @@
+//go:build !shaping
+
+package netxlite
+
+import (
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+)
+
+func TestNewShapingDialer(t *testing.T) {
+	in := &mocks.Dialer{}
+	out := NewMaybeShapingDialer(in)
+	if in != out {
+		t.Fatal("expected to see the same pointer")
+	}
+}