Convert API-checking project to net6.0

Author: blairconrad

tests/SelfInitializingFakes.Tests.Api/ApiApproval.cs

@@ -23,11 +23,11 @@ public class ApiApproval
         [Theory]
         public void ApproveApi(string frameworkVersion)
         {
-            string codeBase = Assembly.GetExecutingAssembly().CodeBase!;
+            string codeBase = Assembly.GetExecutingAssembly().Location;
             UriBuilder uri = new UriBuilder(new Uri(codeBase));
             string assemblyPath = Uri.UnescapeDataString(uri.Path);
             var containingDirectory = Path.GetDirectoryName(assemblyPath);
-            var configurationName = new DirectoryInfo(containingDirectory).Parent.Name;
+            var configurationName = new DirectoryInfo(containingDirectory!).Parent!.Name;
             var assemblyFile = Path.GetFullPath(
                 Path.Combine(
                     GetSourceDirectory(),

tests/SelfInitializingFakes.Tests.Api/SelfInitializingFakes.Tests.Api.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net6.0</TargetFrameworks>
     <AssemblyName>SelfInitializingFakes.Tests.Api</AssemblyName>
   </PropertyGroup>