chore: regenerate README

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Log from Synthtool

2021-04-29 15:40:42,021 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-cloudbuild/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-29 15:40:43,281 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

Full log will be available here:
https://source.cloud.google.com/results/invocations/db9865e8-8af5-44b0-bb67-df70af0e8114/targets

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[yoshi-approver]

Rubber stamped PR!

[codecov]

Codecov Report

Merging #468 (4db0793) into master (6994d33) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #468   +/-   ##
=========================================
  Coverage     82.68%   82.68%           
  Complexity      121      121           
=========================================
  Files             6        6           
  Lines           976      976           
  Branches          3        3           
=========================================
  Hits            807      807           
  Misses          166      166           
  Partials          3        3           

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