Comment the shader template light function by default

This is a minor usability tweak.

The light functions replace the default ones, so even if empty
they will avoid the current shader to have proper lighting and
users will have no idea why.

Code was changed to have the shader function commented by default,
indicating that uncommenting replaces the default function.

(cherry picked from commit c430ff2396d1f7372c88a8ea080ecbf94a43fc9e)

editor/shader_create_dialog.cpp

@@ -175,9 +175,10 @@ void fragment() {
 	// Called for every pixel the material is visible on.
 }
 
-void light() {
+//void light() {
 	// Called for every pixel for every light affecting the material.
-}
+	// Uncomment to replace the default light processing function with this one.
+//}
 )";
 						break;
 					case Shader::MODE_CANVAS_ITEM:
@@ -190,9 +191,10 @@ void fragment() {
 	// Called for every pixel the material is visible on.
 }
 
-void light() {
+//void light() {
 	// Called for every pixel for every light affecting the CanvasItem.
-}
+	// Uncomment to replace the default light processing function with this one.
+//}
 )";
 						break;
 					case Shader::MODE_PARTICLES: