Fix bool varying's generated code will be modified with flat

scene/resources/visual_shader.cpp

@@ -2454,9 +2454,6 @@ void VisualShader::_update_shader() const {
 					global_code += "vec4 ";
 					break;
 				case VaryingType::VARYING_TYPE_BOOLEAN:
-					if (E.value.mode == VaryingMode::VARYING_MODE_VERTEX_TO_FRAG_LIGHT) {
-						global_code += "flat ";
-					}
 					global_code += "bool ";
 					break;
 				case VaryingType::VARYING_TYPE_TRANSFORM: