chore: regenerate README (#371)

This PR was generated using Autosynth. 🌈


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

```
2021-03-02 18:42:18,025 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-document-ai/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-03-02 18:42:18,993 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

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https://source.cloud.google.com/results/invocations/2315047a-ddfe-4f90-89d8-5b1bc03fc5ae/targets

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Author: yoshi-automation

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

@@ -4,14 +4,14 @@
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         "remote": "https://github.com/googleapis/java-document-ai.git",
-        "sha": "e9425d1af5fb7891d2c1e0716a1b45ad9d2b7b5a"
+        "sha": "2f341a10d41f10a35f19eed20c7c6aa891f0569f"
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       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "0199c79b8324fba66476300824aa931788c47e2d"
+        "sha": "21da7d9fa02f6916d9f87cf4072b3547b5c72eb5"
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README.md

@@ -55,12 +55,12 @@ compile 'com.google.cloud:google-cloud-document-ai'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-document-ai:0.4.0'
+compile 'com.google.cloud:google-cloud-document-ai:0.4.1'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-document-ai" % "0.4.0"
+libraryDependencies += "com.google.cloud" % "google-cloud-document-ai" % "0.4.1"
 ```
 
 ## Authentication