chore: regenerate README (#683)

This PR was generated using Autosynth. 🌈


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

```
2021-08-31 22:19:26,488 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dialogflow/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-08-31 22:19:28,820 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/d510dcd1-ba7a-495d-92f4-92014735ba00/targets

- [ ] To automatically regenerate this PR, check this box. (May take up to 24 hours.)

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dialogflow.git",
-        "sha": "4b09ff255a133c28353ae1a309b389086132daf0"
+        "sha": "5fbc3a702d400353ab540cee727243cac0602bb2"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "31728d872f50e439ded2f67fa8d67955b26a4e35"
+        "sha": "9a238a0623879c3de129a376c6085d4a862f6eb9"
       }
     }
   ]

README.md

@@ -51,12 +51,12 @@ If you are using Gradle 5.x or later, add this to your dependencies
 ```Groovy
 implementation platform('com.google.cloud:libraries-bom:22.0.0')
 
-compile 'com.google.cloud:google-cloud-dialogflow'
+implementation 'com.google.cloud:google-cloud-dialogflow'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 
 ```Groovy
-compile 'com.google.cloud:google-cloud-dialogflow:4.1.1'
+implementation 'com.google.cloud:google-cloud-dialogflow:4.1.1'
 ```
 
 If you are using SBT, add this to your dependencies