chore: regenerate README (#300)

This PR was generated using Autosynth. 🌈


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

```
2021-07-27 21:01:46,995 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-workflows/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-27 21:01:48,208 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/34c42788-26e8-4c3b-a3f2-9a5e40b788c3/targets

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-workflows.git",
-        "sha": "704df701e6d2830f01eb8620c15ee841783946d9"
+        "sha": "1915a6a3ced08e3a221463b8bd2b6c7e45862e78"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "e44dc0c742b1230887a73552357e0c18dcc30b92"
+        "sha": "3d32990b6f4b57be77455e3ca89e6e21cd0c06b3"
       }
     }
   ]