oslo.serialization 2.29.3 release

meta:version: 2.29.3
meta:diff-start: -
meta:series: train
meta:release-type: release
meta:pypi: yes
meta:first: no
meta:release:Author: Daniel Bengtsson <dbengt@redhat.com>
meta:release:Commit: Daniel Bengtsson <dbengt@redhat.com>
meta:release:Change-Id: Ic2b688e234b92a5e98e617531323738a51db7151
meta:release:Code-Review+2: Hervé Beraud <hberaud@redhat.com>
meta:release:Code-Review+2: Sean McGinnis <sean.mcginnis@gmail.com>
meta:release:Workflow+1: Sean McGinnis <sean.mcginnis@gmail.com>