message: [C#] Fix FlatBuffers.Tests when ENABLE_SPAN_T is defined
  There is a test code error that causes the CanReadCppGeneratedWireFile test to fail when ENABLE_SPAN_T is defined. When TestarrayofboolsLength is not 0, then the GetTestarrayofboolsBytes() should have a length.
diff: @@ -258,7 +258,7 @@ namespace FlatBuffers.Test
  }
  else
  {
  - Assert.IsTrue(monster.GetTestarrayofboolsBytes().Length == 0);
  + Assert.IsTrue(monster.GetTestarrayofboolsBytes().Length != 0);
  }
  #else
  var nameBytes = monster.GetNameBytes().Value;
  