chore(python): bump idna from 3.4 to 3.7 in .kokoro (#640)

Source-Link: https://github.com/googleapis/synthtool/commit/d50980e704793a2d3310bfb3664f3a82f24b5796
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:5a4c19d17e597b92d786e569be101e636c9c2817731f80a5adec56b2aa8fe070

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