Remove obsolete VMap forward declaration.

Author: Ivorforce

scene/resources/visual_shader.h

@@ -38,9 +38,6 @@
 class VisualShaderNodeParameter;
 class VisualShaderNode;
 
-template <typename T, typename V>
-class VMap;
-
 class VisualShader : public Shader {
 	GDCLASS(VisualShader, Shader);