Update test project dependencies

Author: jnm2

src/AmbientTasks.Tests/AmbientTasks.Tests.csproj

@@ -6,11 +6,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="AltCover" Version="7.3.806" />
-    <PackageReference Include="nunit" Version="3.12.0" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.16.1" PrivateAssets="all" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
-    <PackageReference Include="Shouldly" Version="3.0.2" />
+    <PackageReference Include="AltCover" Version="8.6.68" />
+    <PackageReference Include="nunit" Version="3.13.3" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
+    <PackageReference Include="Shouldly" Version="4.2.1" />
   </ItemGroup>
 
   <ItemGroup>

src/AmbientTasks.Tests/AmbientTasksPostTests.cs

@@ -413,7 +413,7 @@ public static void Subsequent_invocations_by_SynchronizationContext_are_ignored_
             }
 
             callCount.ShouldBe(0);
-            Should.Throw<Exception>(postedAction);
+            Should.Throw<Exception>(postedAction!);
             callCount.ShouldBe(1);
 
             postedAction.ShouldNotBeNull();

src/AmbientTasks.Tests/RequireOnAllTestMethodsAttribute.cs

@@ -21,7 +21,7 @@ public void BeforeTest(ITest test)
         {
             var missingTypes = attributeTypes
                 .Except(
-                    from data in test.Method.MethodInfo.GetCustomAttributesData()
+                    from data in test.Method!.MethodInfo.GetCustomAttributesData()
                     select data.AttributeType)
                 .ToList();