chore(python): update .kokoro/requirements.txt (#431)

Source-Link: https://github.com/googleapis/synthtool/commit/703554a14c7479542335b62fa69279f93a9e38ec
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:94961fdc5c9ca6d13530a6a414a49d2f607203168215d074cdb0a1df9ec31c0b

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
2 files changed