chore: regenerate README (#391)

This PR was generated using Autosynth. 🌈


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

```
2021-01-06 21:52:53,378 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dlp/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-01-06 21:52:54,239 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/cc3eb0c2-4f5a-4aa2-b61d-ad12371ecfcb/targets

- [ ] To automatically regenerate this PR, check this box.

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dlp.git",
-        "sha": "3acf4b02aeba1e7c51df74c031ec355608d624c9"
+        "sha": "76b67ecdb1a95979399a496a536f10f91a1aebc3"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "996775eca5fd934edac3c2ae34b80ff0395b1717"
+        "sha": "a3e990f3545dc8ccd384a75d20ce9cb185ca6a28"
       }
     }
   ]

README.md

@@ -39,15 +39,22 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-dlp</artifactId>
-  <version>2.2.3</version>
+  <version>2.2.4</version>
 </dependency>
 
 ```
 
-If you are using Gradle, add this to your dependencies
+If you are using Gradle 5.x or later, add this to your dependencies
+```Groovy
+implementation platform('com.google.cloud:libraries-bom:16.2.0')
+
+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:2.2.4'
 ```
+
 If you are using SBT, add this to your dependencies
 ```Scala
 libraryDependencies += "com.google.cloud" % "google-cloud-dlp" % "2.2.4"