chore: regenerate README (#230)

This PR was generated using Autosynth. 🌈


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

```
2021-04-12 16:04:29,357 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-workflows/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-12 16:04:30,611 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/ce835c94-b111-4266-90fa-01a8feebe5f0/targets

- [ ] To automatically regenerate this PR, check this box. (May take up to 24 hours.)

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-workflows.git",
-        "sha": "c3cef693a677061fcb1b1585bebe1fa2c39b4ed9"
+        "sha": "201bc199974d067485585af561c7974a98eb73c5"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "d9ddac83a22a600dd33854c9d835a4fe52284207"
+        "sha": "0a071b3460344886297a304253bf924aa68ddb7e"
       }
     }
   ]

README.md

@@ -20,7 +20,7 @@ If you are using Maven, add this to your pom.xml file:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-workflows</artifactId>
-  <version>0.3.0</version>
+  <version>0.3.1</version>
 </dependency>
 
 ```