Add doc comment explaining EnableDefaultCssItems in Blazor templates (dotnet#33845)

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### Description of Change

Add a doc comment to the maui blazor template as a follow-up to
dotnet#33718 (comment)

### Issues Fixed

dotnet#33718

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: akoeplinger <1376924+akoeplinger@users.noreply.github.com>

Author: akoeplinger

src/Templates/src/templates/maui-blazor-solution/MauiApp.1/MauiApp.1.csproj

@@ -17,6 +17,7 @@
     <UseMaui>true</UseMaui>
     <SingleProject>true</SingleProject>
     <ImplicitUsings>enable</ImplicitUsings>
+    <!-- Disable MAUI CSS handling so Blazor can handle it -->
     <EnableDefaultCssItems>false</EnableDefaultCssItems>
     <Nullable>enable</Nullable>
 

src/Templates/src/templates/maui-blazor/MauiApp.1.csproj

@@ -17,6 +17,7 @@
         <UseMaui>true</UseMaui>
         <SingleProject>true</SingleProject>
         <ImplicitUsings>enable</ImplicitUsings>
+        <!-- Disable MAUI CSS handling so Blazor can handle it -->
         <EnableDefaultCssItems>false</EnableDefaultCssItems>
         <Nullable>enable</Nullable>