chore: regenerate README (googleapis#567)

This PR was generated using Autosynth. 🌈


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

```
2021-07-27 23:40:34,947 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 23:40:36,238 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/92a5a47e-f6f5-4db6-9bf1-945a247a23a3/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": "5139e9345f113e460419d369880fce04fb8a9593"
+        "sha": "20441f5bd07ca8e55ccc352393ebb97727ea4bd0"
       }
     },
     {