chore: regenerate README (#507)

This PR was generated using Autosynth. 🌈


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

```
2021-04-12 15:33:54,424 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dataproc/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-12 15:33:55,677 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/a6e6160a-29f8-4ae5-9911-555262401c5e/targets

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

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dataproc.git",
-        "sha": "a4e962acaa7a401c8934c99b0d16a3825d372e81"
+        "sha": "23d3a4280c373f068132632f14d455c1ee3eaf22"
       }
     },
     {

README.md

@@ -17,7 +17,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>19.2.1</version>
+      <version>20.0.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -39,7 +39,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-dataproc</artifactId>
-  <version>1.3.0</version>
+  <version>1.4.0</version>
 </dependency>
 
 ```