golang: qq: Don't depend on six

Just use builtins and cimported things that we have at pyx level.

golang/_golang.pyx

@@ -770,7 +770,6 @@ cdef DType parse_dtype(dtype) except <DType>-1:
 # ---- strings ----
 
 from golang import strconv as pystrconv
-import six
 
 def pyb(s): # -> bytes
     """b converts str/unicode/bytes s to UTF-8 encoded bytestring.
@@ -821,14 +820,14 @@ def pyqq(obj):
     # make sure obj is text | bytes
     # py2: unicode | str
     # py3: str     | bytes
-    if not isinstance(obj, (six.text_type, six.binary_type)):
+    if not isinstance(obj, (unicode, bytes)):
         obj = str(obj)
 
     qobj = pystrconv.quote(obj)
 
     # `printf('%s', qq(obj))` should work. For this make sure qobj is always a
     # str - not bytes under py3 (if it was bytes it will print e.g. as b'...')
-    if six.PY3:
+    if PY_MAJOR_VERSION >= 3:
         qobj = pyu(qobj)
 
     return qobj