chore: regenerate README

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Log from Synthtool

2020-12-10 00:02:28,845 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-secretmanager/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2020-12-10 00:02:29,725 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

Full log will be available here:
https://source.cloud.google.com/results/invocations/1ff5f3b1-409d-482a-aa84-30bc8ae7c55d/targets

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[yoshi-approver]

Rubber stamped PR!

[codecov]

Codecov Report

Merging #322 (86e8c20) into master (a12860d) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #322   +/-   ##
=========================================
  Coverage     77.50%   77.50%           
  Complexity      220      220           
=========================================
  Files            12       12           
  Lines          1698     1698           
  Branches         22       22           
=========================================
  Hits           1316     1316           
  Misses          348      348           
  Partials         34       34           

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