chore: regenerate README (#258)

This PR was generated using Autosynth. 🌈


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

```
2021-09-01 22:51:14,851 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-pubsublite-spark/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-09-01 22:51:15,797 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/a1e0c28e-f185-4be4-97cc-dbce3e11f79b/targets

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

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsublite-spark.git",
-        "sha": "949b2c0dc00344cd9fba9a7113e9ea11b511cf88"
+        "sha": "1dc47d6661dccad188861b10f9c563be41a21d6c"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "6252f2cd074c38f37b44abe5e96d128733eb1b61"
+        "sha": "5c0fa62eea9c33ebe61e582424b659eb264e1ba4"
       }
     }
   ]

README.md

@@ -29,7 +29,7 @@ If you are using Maven, add this to your pom.xml file:
 If you are using Gradle without BOM, add this to your dependencies
 
 ```Groovy
-compile 'com.google.cloud:pubsublite-spark-sql-streaming:0.3.1'
+implementation 'com.google.cloud:pubsublite-spark-sql-streaming:0.3.1'
 ```
 
 If you are using SBT, add this to your dependencies