message: test: enable select stack height validation tests
diff: using namespace fizzy;
  using namespace fizzy::test;
  -TEST(validation_stack, DISABLED_select_stack_underflow)
  +TEST(validation_stack, select_stack_underflow)
  {
  /* wat2wasm --no-check
  (func
  @@ -24,7 +24,7 @@ TEST(validation_stack, DISABLED_select_stack_underflow)
  EXPECT_THROW_MESSAGE(parse(wasm), validation_error, "stack underflow");
  }
  -TEST(validation_stack_type, DISABLED_select_stack_underflow_2)
  +TEST(validation_stack_type, select_stack_underflow_2)
  {
  /* wat2wasm --no-check
  (func (param i32) (result i32)
  