Updated an inaccurate comment.

Tests can run nearly as fast under PostgreSQL and MySQL as under SQLite
with a bit of configuration and the speedup is always a good thing.

tests/test_sqlite.py

@@ -22,9 +22,8 @@ DATABASES = {
 }
 
 SECRET_KEY = "django_tests_secret_key"
-# To speed up tests under SQLite we use the MD5 hasher as the default one. 
-# This should not be needed under other databases, as the relative speedup
-# is only marginal there.
+
+# Use a fast hasher to speed up tests.
 PASSWORD_HASHERS = (
     'django.contrib.auth.hashers.MD5PasswordHasher',
 )