chore: regenerate README (#468)
chore: regenerate README (#468)

This PR was generated using Autosynth. :rainbow:


<details><summary>Log from Synthtool</summary>

```
2021-07-27 22:14:26,309 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-billing/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-27 22:14:27,510 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

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https://source.cloud.google.com/results/invocations/4fcffadd-0469-40d4-bc26-f5413519a75e/targets

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