chore: regenerate README (#483)

This PR was generated using Autosynth. 🌈


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

```
2021-05-14 02:15:06,952 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-document-ai/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-05-14 02:15:08,178 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/cbc0aa8f-d937-461e-9e67-b0feb4589ea1/targets

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-document-ai.git",
-        "sha": "402d7ca1808b814f12adac2c86676b89222fb3fa"
+        "sha": "6f9e49beaa0dad41fc044f883f4eb213696e533c"
       }
     },
     {

README.md

@@ -31,7 +31,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
   <dependency>
     <groupId>com.google.cloud</groupId>
     <artifactId>google-cloud-document-ai</artifactId>
-    <version>0.8.0</version>
+    <version>0.8.2</version>
   </dependency>
 
 ```
@@ -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-document-ai</artifactId>
-  <version>0.8.0</version>
+  <version>0.8.2</version>
 </dependency>
 
 ```