msvc: Do not define DEBUG for debug builds

It is not used anywhere and causes a warning about redefinition because
it is used in modutimeq.c

windows/msvc/debug.props

@@ -4,10 +4,6 @@
   <PropertyGroup Label="UserMacros" />
   <PropertyGroup>
   </PropertyGroup>
-  <ItemDefinitionGroup>
-    <ClCompile>
-      <PreprocessorDefinitions>DEBUG;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-    </ClCompile>
-  </ItemDefinitionGroup>
+  <ItemDefinitionGroup />
   <ItemGroup />
 </Project>
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