Fix T62882: Make Dynamic Paint update weights in viewport

Related to T62882
When the SupportsMapping modifier flag was added to the dynamic paint
modifier it was added commented out. It may have not worked back then,
but it seems to work fine now.
MOD_weightvgedit.c was already updated similarly.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D6072

source/blender/modifiers/intern/MOD_dynamicpaint.c

@@ -178,7 +178,7 @@ ModifierTypeInfo modifierType_DynamicPaint = {
     /* structSize */ sizeof(DynamicPaintModifierData),
     /* type */ eModifierTypeType_Constructive,
     /* flags */ eModifierTypeFlag_AcceptsMesh |
-        /*                          eModifierTypeFlag_SupportsMapping |*/
+        eModifierTypeFlag_SupportsMapping |
         eModifierTypeFlag_UsesPointCache | eModifierTypeFlag_Single |
         eModifierTypeFlag_UsesPreview,