test/binding.rb: remove a duplicated test.

mrbgems/mruby-binding/test/binding.rb

@@ -43,13 +43,6 @@ assert("Binding#local_variable_get") do
   }
 end
 
-assert("Binding#source_location") do
-  skip unless -> {}.source_location
-
-  bind, source_location = binding, [__FILE__, __LINE__]
-  assert_equal source_location, bind.source_location
-end
-
 assert "Kernel#binding and .eval from C" do
   bind = binding_in_c
   assert_equal 5, bind.eval("2 + 3")