Exclude Exceptions folder from build

Add a <Compile Remove> entry to src/WinRT.Runtime2/WinRT.Runtime.csproj to exclude Exceptions/**/*.cs from compilation. This matches other implementation-only folders removed from the project (e.g. ABI, InteropServices) to minimize the number of code changes and reduce the build surface.

Author: Sergio0694

src/WinRT.Runtime2/WinRT.Runtime.csproj

@@ -140,6 +140,7 @@
       <Compile Remove="ABI\**\*.cs"/>
 
       <!-- Also remove other folders with implementation-only types, to minimize the number of code changes needed -->
+      <Compile Remove="Exceptions\**\*.cs"/>
       <Compile Remove="InteropServices\AsyncInfo\**\*.cs"/>
       <Compile Remove="InteropServices\Bindables\**\*.cs"/>
       <Compile Remove="InteropServices\Buffers\**\*.cs"/>