chore: regenerate README (#666)

This PR was generated using Autosynth. 🌈


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

```
2021-08-24 23:12:27,839 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dialogflow/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-08-24 23:12:29,039 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/56f2be70-2d52-4006-8e12-d7f48731457c/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-dialogflow.git",
-        "sha": "5b91069c5f3feeac01fdf8d328f86927efd12ab1"
+        "sha": "3c1cbbb7e5870ffbb58ffda32a0bbea73e510ab6"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "a01e1a0bf70754f51450958b966bd673945d1e6e"
+        "sha": "63cff634aabb85854caa511c5837ea6b45f42b4b"
       }
     }
   ]

README.md

@@ -41,7 +41,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-dialogflow</artifactId>
-  <version>3.3.0</version>
+  <version>4.1.0</version>
 </dependency>
 
 ```