chore: regenerate README (googleapis#561)

This PR was generated using Autosynth. 🌈


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

```
2021-07-27 22:31:03,756 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-resourcemanager/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-27 22:31:05,090 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/277cd198-eed0-4ec6-8851-291d822afcb3/targets

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java-resourcemanager/.github/readme/synth.metadata/synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-resourcemanager.git",
-        "sha": "993c3b374046b565d39f5cdafba432154d38aa60"
+        "sha": "53e483b2cbb7c9640b1ec2b509b2288affb575eb"
       }
     },
     {