[tests] make clean import in test_compress.py

I don't remember the reason of this previous direct import.

test/test_compress.py

@@ -5,7 +5,7 @@ import random
 from cubicweb.devtools.testlib import CubicWebTC
 from logilab.common import date
 
-from utils import compress_old_hits
+from cubes.awstats.utils import compress_old_hits
 
 
 class CompressTest(CubicWebTC):

test/utils.py

-../utils.py
\ No newline at end of file