chore: regenerate README (#59)

This PR was generated using Autosynth. 🌈


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

```
2021-02-26 01:26:08,834 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-retail/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-02-26 01:26:10,423 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/9549342c-e770-464c-b214-29e9d01c7385/targets

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-retail.git",
-        "sha": "f04501fdac508979e2bc5c575a012ad3ba14098c"
+        "sha": "d64d51c162b2005a29d011cf2042bcbb6de9b4d8"
       }
     },
     {

README.md

@@ -20,19 +20,19 @@ If you are using Maven, add this to your pom.xml file:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-retail</artifactId>
-  <version>0.1.1</version>
+  <version>0.2.1</version>
 </dependency>
 
 ```
 
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-retail:0.2.0'
+compile 'com.google.cloud:google-cloud-retail:0.2.1'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-retail" % "0.2.0"
+libraryDependencies += "com.google.cloud" % "google-cloud-retail" % "0.2.1"
 ```
 
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