chore: regenerate README (#501)

This PR was generated using Autosynth. 🌈


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

```
2021-04-20 20:50:19,978 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-logging/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-20 20:50:21,250 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/8098741b-34f9-4b2b-aaf4-8290ae3de4d3/targets

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Author: yoshi-automation

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-logging.git",
-        "sha": "70c0c0c8fa840d3cd91230e6ec8993d244578249"
+        "sha": "7a57aa5957be2928a5e948b0972d7ccf028635ed"
       }
     },
     {

README.md

@@ -39,7 +39,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-logging</artifactId>
-  <version>2.2.0</version>
+  <version>2.2.1</version>
 </dependency>
 
 ```