chore: regenerate README (#450)

This PR was generated using Autosynth. 🌈


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

```
2021-02-23 00:38:23,818 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-storage-nio/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-02-23 00:38:25,366 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/e8c52cbd-2b36-41ab-9bb6-e5bba89f89a7/targets

- [ ] To automatically regenerate this PR, check this box.

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-storage-nio.git",
-        "sha": "75a9374cd64834bf168444f8a720cb303c28766d"
+        "sha": "7e74e1fb24ca9f0bd0a6fe1175582cb52088c970"
       }
     },
     {

README.md

@@ -42,7 +42,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-nio</artifactId>
-  <version>0.122.5</version>
+  <version>0.122.7</version>
 </dependency>
 
 ```