chore: regenerate README (#98)

This PR was generated using Autosynth. 🌈


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

```
2021-07-27 23:45:49,713 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-artifact-registry/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-27 23:45:50,978 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

Full log will be available here:
https://source.cloud.google.com/results/invocations/2df616b6-c089-4781-addf-c1b31af7367a/targets

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.github/readme/synth.metadata/synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-artifact-registry.git",
-        "sha": "33bb4ca789c09363748782503e2f3f7b67bda8e2"
+        "sha": "cbaa9f5a63ef890c207427e06553e546dd804a2d"
       }
     },
     {