fix test

Author: smdn

tests/Smdn.Reflection.ReverseGenerating.ListApi.Core/Smdn.Reflection.ReverseGenerating.ListApi/AssemblyLoader.cs

@@ -37,10 +37,14 @@ public void Init()
     logger = services.BuildServiceProvider().GetService<ILoggerFactory>()?.CreateLogger("test");
   }
 
+#if NETCOREAPP3_1_OR_GREATER
   [TestCase(true, "netstandard2.1")]
   [TestCase(false, "netstandard2.1")]
+#endif
+#if NET5_0_OR_GREATER
   [TestCase(true, "net5.0")]
   [TestCase(false, "net5.0")]
+#endif
   public void UsingAssembly(bool loadIntoReflectionOnlyContext, string targetFrameworkMoniker)
   {
     var assemblyFile = new FileInfo(
@@ -90,10 +94,14 @@ public void UsingAssembly(bool loadIntoReflectionOnlyContext, string targetFrame
     Assert.IsTrue(unloaded, nameof(unloaded));
   }
 
+#if NETCOREAPP3_1_OR_GREATER
   [TestCase(true, "netstandard2.1")]
   [TestCase(false, "netstandard2.1")]
+#endif
+#if NET5_0_OR_GREATER
   [TestCase(true, "net5.0")]
   [TestCase(false, "net5.0")]
+#endif
   public void UsingAssembly_ResolveDependency(bool loadIntoReflectionOnlyContext, string targetFrameworkMoniker)
   {
     var assemblyFile = new FileInfo(