chore: regenerate README (googleapis#309)

This PR was generated using Autosynth. 🌈


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

```
2020-12-03 18:10:39,031 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-storage-nio/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2020-12-03 18:10:39,902 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/d8a1877c-da27-4e6d-bca8-ff6ff0a78131/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": "e88e3f0ba2b847edd52b271063184af2dbafae9b"
+        "sha": "2f6eb31abe049ca69dc43506d7a62bd6cc47d905"
       }
     },
     {

README.md

@@ -20,7 +20,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>15.0.0</version>
+      <version>16.1.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>