chore: regenerate README

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Log from Synthtool

2021-07-27 21:32:12,840 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-cloudbuild/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-27 21:32:14,167 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

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