Remove empty Package Content sections from project files

Co-authored-by: Keboo <952248+Keboo@users.noreply.github.com>

Author: Copilot

src/MaterialDesignColors.Wpf/MaterialDesignColors.Wpf.csproj

@@ -25,9 +25,5 @@
       <_Parameter2>$(MDIXColorsVersion)</_Parameter2>
     </AssemblyAttribute>
   </ItemGroup>
-  
-  <!-- Package Content -->
-  <ItemGroup>
-    <!-- No additional package content needed - inherited from Directory.Build.props -->
-  </ItemGroup>
+
 </Project>

src/MaterialDesignThemes.MahApps/MaterialDesignThemes.MahApps.csproj

@@ -24,9 +24,5 @@
   <ItemGroup>
     <PackageReference Include="MahApps.Metro" />
   </ItemGroup>
-  
-  <!-- Package Content -->
-  <ItemGroup>
-    <!-- Common content inherited from Directory.Build.props -->
-  </ItemGroup>
+
 </Project>