chore: regenerate README (#581)

This PR was generated using Autosynth. 🌈


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

```
2021-06-03 00:22:11,156 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-storage-nio/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-06-03 00:22:12,333 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/46d523a3-d180-42d1-a192-46ab78e692ee/targets

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-storage-nio.git",
-        "sha": "eae323d3373fe21deaf3b636834511defc6bb348"
+        "sha": "35f406ecd2ffd63836875de1dc24870592c9c3a7"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "c3e41da0fa256ad7f6b4bc76b9d069dedecdfef4"
+        "sha": "811d20bc0b00c09773dfc74ac2baaf1286e943b7"
       }
     }
   ]

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>0.123.0</version>
+  <version>0.123.1</version>
 </dependency>
 
 ```
@@ -55,12 +55,12 @@ compile 'com.google.cloud:google-cloud-nio'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-nio:0.123.0'
+compile 'com.google.cloud:google-cloud-nio:0.123.1'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-nio" % "0.123.0"
+libraryDependencies += "com.google.cloud" % "google-cloud-nio" % "0.123.1"
 ```
 
 ## Authentication