golang: test_method -> test_func

@method(cls) was deprecated and removed in favour of @func(cls) in
942ee900 (golang: Deprecate @method(cls) in favour of @func(cls)) and
262f8986 (golang: Kill @method). The test name was overlooked.

golang/golang_test.py

@@ -480,7 +480,7 @@ def _test_blockforever():
     with raises(BlocksForever): select((z.send, 1), z.recv)
 
 
-def test_method():
+def test_func():
     # test how @func(cls) works
     # this also implicitly tests just @func, since @func(cls) uses that.