chore: regenerate README (#133)

This PR was generated using Autosynth. 🌈


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

```
2021-04-06 19:56:10,679 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-pubsublite-spark/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-06 19:56:11,940 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/3eb00cbc-2c38-4d6d-90de-0da91cf5243b/targets

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsublite-spark.git",
-        "sha": "1bf772a275e76d6b7229d628b72d5dce4f5c8bc5"
+        "sha": "98f5863245584bf517d4817610dcca0c3979a470"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "e5fa6d93e42918dd4a000a80b92be23f5f4c6ac7"
+        "sha": "705743e66f5c0b24a95f7f30619c9d3ef747b317"
       }
     }
   ]

README.md

@@ -176,6 +176,7 @@ has instructions for running the samples.
 | --------------------------- | --------------------------------- | ------ |
 | Admin Utils | [source code](https://github.com/googleapis/java-pubsublite-spark/blob/master/samples/snippets/src/main/java/pubsublite/spark/AdminUtils.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-pubsublite-spark&page=editor&open_in_editor=samples/snippets/src/main/java/pubsublite/spark/AdminUtils.java) |
 | Publish Words | [source code](https://github.com/googleapis/java-pubsublite-spark/blob/master/samples/snippets/src/main/java/pubsublite/spark/PublishWords.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-pubsublite-spark&page=editor&open_in_editor=samples/snippets/src/main/java/pubsublite/spark/PublishWords.java) |
+| Read Results | [source code](https://github.com/googleapis/java-pubsublite-spark/blob/master/samples/snippets/src/main/java/pubsublite/spark/ReadResults.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-pubsublite-spark&page=editor&open_in_editor=samples/snippets/src/main/java/pubsublite/spark/ReadResults.java) |
 | Word Count | [source code](https://github.com/googleapis/java-pubsublite-spark/blob/master/samples/snippets/src/main/java/pubsublite/spark/WordCount.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-pubsublite-spark&page=editor&open_in_editor=samples/snippets/src/main/java/pubsublite/spark/WordCount.java) |