chore: regenerate README (#55)

This PR was generated using Autosynth. 🌈


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

```
2021-01-27 18:03:53,233 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-pubsublite-kafka/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-01-27 18:03:54,138 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/3d843b7c-d7ed-491e-a687-aaf8b433bcee/targets

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsublite-kafka.git",
-        "sha": "263ed6ad642454d82f0d8954461826a4e3af81ed"
+        "sha": "c75c9c1f8339543cc34514e1be75fb8427975366"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "b259489b06b25f399768b74b8baa943991f38ea7"
+        "sha": "57c23fa5705499a4181095ced81f0ee0933b64f6"
       }
     }
   ]

README.md

@@ -55,20 +55,9 @@ to add `pubsublite-kafka` as a dependency in your code.
 
 ## About Pub/Sub Lite Kafka Shim
 
-[Google Pub/Sub Lite][product-docs] is designed to provide reliable,
-many-to-many, asynchronous messaging between applications. Publisher
-applications can send messages to a topic and other applications can
-subscribe to that topic to receive the messages. By decoupling senders and
-receivers, Google Cloud Pub/Sub allows developers to communicate between
-independently written applications. See the
-[Google Pub/Sub Lite docs](https://cloud.google.com/pubsub/quickstart-console#before-you-begin)
-for more details on how to activate Pub/Sub Lite for your project, as well as
-guidance on how to choose between Cloud Pub/Sub and Pub/Sub Lite.
-
-Compared to Google Pub/Sub, Pub/Sub Lite provides partitioned zonal data
-storage with predefined capacity. This means a large portion of the Kafka
-Producer/Consumer API can be implemented using Pub/Sub Lite as a backend. The
-key differences are:
+Because [Google Cloud Pub/Sub Lite][product-docs] provides partitioned zonal data storage with
+predefined capacity, a large portion of the Kafka Producer/Consumer API can
+be implemented using Pub/Sub Lite as a backend. The key differences are:
 - Pub/Sub Lite does not support transactions. All transaction methods on
   `Producer<byte[], byte[]>` will raise an exception.
 - Producers operate on a single topic, and Consumers on a single subscription.