chore: regenerate README

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Log from Synthtool

2021-05-13 14:04:53,725 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-container/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-05-13 14:04:54,945 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

Full log will be available here:
https://source.cloud.google.com/results/invocations/6b5f7b1f-2679-45a1-b40a-bca8001078fd/targets

• To automatically regenerate this PR, check this box. (May take up to 24 hours.)

[yoshi-approver]

Rubber stamped PR!

[codecov]

Codecov Report

Merging #451 (6c63742) into master (ab59387) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #451   +/-   ##
=========================================
  Coverage     87.04%   87.04%           
  Complexity      238      238           
=========================================
  Files             7        7           
  Lines          1667     1667           
  Branches          3        3           
=========================================
  Hits           1451     1451           
  Misses          214      214           
  Partials          2        2           

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