chore: regenerate README (#492)

This PR was generated using Autosynth. 🌈


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

```
2021-04-13 12:19:40,367 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dlp/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-13 12:19:41,780 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/8206bd35-44fd-47e4-a030-548e64df5f12/targets

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Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dlp.git",
-        "sha": "c40120a958ea8d6056768a1ccc862448f79876b8"
+        "sha": "5924f7a10860aa46443b0da5988a45440e547cfb"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "0a071b3460344886297a304253bf924aa68ddb7e"
+        "sha": "082e1ca0863b13ada8594fe91845380765da5b70"
       }
     }
   ]

README.md

@@ -52,12 +52,12 @@ compile 'com.google.cloud:google-cloud-dlp'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-dlp:2.3.0'
+compile 'com.google.cloud:google-cloud-dlp:2.3.1'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-dlp" % "2.3.0"
+libraryDependencies += "com.google.cloud" % "google-cloud-dlp" % "2.3.1"
 ```
 
 ## Authentication