chore: regenerate README (#282)

This PR was generated using Autosynth. 🌈


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

```
2021-08-11 21:16:14,989 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dialogflow-cx/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-08-11 21:16:16,238 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

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https://source.cloud.google.com/results/invocations/4e1ebb25-e1d1-4543-9625-84470a7631bc/targets

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feat!: release gapic-generator-java v2.0.0

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dialogflow-cx.git",
-        "sha": "40571343d51c2275a556a2a45508c014f2e9aee1"
+        "sha": "6b2152a0fff0dc1ddee98688b511d55679eba728"
       }
     },
     {