removed old chapter 20 no compile csproj references
MODIFY
src/Chapter20/Chapter20.csproj
src/Chapter20/Chapter20.csproj
<Compile Include="..\Shared\PiCalculator.cs">
<Link>PiCalculator.cs</Link>
</Compile>
- <None Include="Listing20.07.SignaturesOfAsyncEnumerableSelectMethods.cs" />
- <None Include="Listing20.13.SynchronousHighLatencyInvocationInWPF.cs" />
<None Include="Listing20.14.SynchronousHighLatencyInvocationInWPF.cs" />
- <None Include="Listing20.14.SynchronousHighLatencyInvocationInWPFUsingAwait.cs" />
- <None Include="Listing20.15.IteratingOverAwaitOperation.cs" />
<None Include="Listing20.15.SynchronousHighLatencyInvocationInWPFUsingAwait.cs" />
<None Include="Listing20.16.IteratingOverAwaitOperation.cs" />
<PackageReference Include="System.Linq.Async" Version="4.0.0" />

removed old chapter 20 no compile csproj references