Clarify build optimize rule

Directory.Build.props

@@ -18,11 +18,10 @@
   <!-- Import the shared global .props file -->
   <Import Project="$(MSBuildThisFileDirectory)shared-infrastructure\msbuild\props\SixLabors.Global.props" />
 
-  <!-- Custom Project Configuration doesn't seem to copy this setting properly. -->
-  <PropertyGroup Condition="$(Configuration.StartsWith('Debug')) == true">
-    <Optimize>false</Optimize>
-  </PropertyGroup>
-
+  <!--
+  Ensure all custom build configurations based upon "Release" are optimized.
+  This is easier than setting each project individually.
+  -->
   <PropertyGroup Condition="$(Configuration.StartsWith('Release')) == true">
     <Optimize>true</Optimize>
   </PropertyGroup>