[python] Bump Cython version

Build with Cython 0.25.2 fails on Python 3.7.5, 0.27.2 fails with a
different error.

In some other project the fix was to upgrade to 0.29.2 which worked, but
decided to use latest 0.29 as there are lots of bug fixes which may or
may not be useful.

Change-Id: Ida81e06917c0f12619fe53764026bc1764027e22
Reviewed-on: http://gerrit.cloudera.org:8080/14883
Reviewed-by: Adar Dembo <adar@cloudera.com>
Tested-by: Kudu Jenkins
Reviewed-by: Grant Henke <granthenke@apache.org>
1 file changed