chore: regenerate README (#278)

This PR was generated using Autosynth. 🌈


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

```
2021-05-17 23:22:58,272 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-os-config/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-05-17 23:22:59,628 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/6bcf71b0-404c-4c42-af22-65662f3baddf/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-os-config.git",
-        "sha": "d8e2d3edf23247828ceaef92dfe0b39423d87c38"
+        "sha": "afd434b1a578de63f22b4ccc77b728b21159072b"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "6244244abd0da5ef750e3bbb63fa22ec6803b4db"
+        "sha": "c86c7a60985644eab557949363a38301d40d78d2"
       }
     }
   ]

README.md

@@ -17,18 +17,18 @@ If you are using Maven, add this to your pom.xml file:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-os-config</artifactId>
-  <version>1.2.2</version>
+  <version>1.2.3</version>
 </dependency>
 ```
 
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-os-config:1.2.2'
+compile 'com.google.cloud:google-cloud-os-config:1.2.3'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-os-config" % "1.2.2"
+libraryDependencies += "com.google.cloud" % "google-cloud-os-config" % "1.2.3"
 ```
 
 ## Authentication