chore: regenerate README (#101)

This PR was generated using Autosynth. 🌈


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

```
2021-02-26 22:52:17,406 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-pubsublite-spark/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-02-26 22:52:18,972 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

Full log will be available here:
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.github/readme/synth.metadata/synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsublite-spark.git",
-        "sha": "9187ff382714b810e94758f3ba1e89a75ae99caf"
+        "sha": "f82087b17a6c6e44af235a7e6e7a4632874aef42"
       }
     },
     {

README.md

@@ -85,8 +85,7 @@ and manual Spark installations.
 
 ## Downloading and Using the Connector
 
-<!--- TODO(jiangmichael): Release on Maven Central and add Maven Central link -->
-  The connector will be available from the Maven Central repository. It can be used using the `--packages` option or the `spark.jars.packages` configuration property.
+  The connector is available from the [Maven Central repository](https://search.maven.org/artifact/com.google.cloud/pubsublite-spark-sql-streaming). You can download and pass it in the `--packages` option when using the `spark-submit` command or set it via the `spark.jars.packages` [configuration property](https://spark.apache.org/docs/latest/configuration.html#available-properties).
 
 ## Compatibility
 | Connector version | Spark version |