Removed python2 code in imaputil

This code is marked as python2, could be removed.

offlineimap/imaputil.py

@@ -128,13 +128,7 @@ def imapsplit(imapstring):
             retval.append(quoted)
             workstr = rest
         else:
-            splits = None
-            # Python2
-            if hasattr(string, 'split'):
-                splits = string.split(workstr, maxsplit = 1)
-            # Python3
-            else:
-                splits = str.split(workstr, maxsplit = 1)
+            splits = str.split(workstr, maxsplit=1)
             splitslen = len(splits)
             # The unquoted word is splits[0]; the remainder is splits[1]
             if splitslen == 2: