(cake-contrib/Cake.DotNetTool.Module#40) Only target one framework

This is known issue with Cake, that will hopefully be addressed in the
future.

Author: gep13

Source/Cake.DotNetTool.Module/Cake.DotNetTool.Module.csproj

@@ -1,6 +1,6 @@
  <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net50;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <IncludeSymbols>true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>