chore: regenerate README (#559)

This PR was generated using Autosynth. 🌈


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

```
2021-03-19 13:56:19,706 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-pubsublite/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-03-19 13:56:20,613 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/99cd9296-4c2a-4e5a-8f1e-ce009556f502/targets

- [ ] To automatically regenerate this PR, check this box.

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsublite.git",
-        "sha": "9f53f6a6699acdd64e1c5ed7cc0b7495209e2548"
+        "sha": "2f3e1156b17eb7d09788326caa4d9c33c6bf468e"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "78437c732a60c64895778697b078497b0988346c"
+        "sha": "8b13da943497f75c5303700bff5aabdd85d939e0"
       }
     }
   ]

README.md

@@ -20,7 +20,7 @@ If you are using Maven, add this to your pom.xml file:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-pubsublite</artifactId>
-  <version>0.11.1</version>
+  <version>0.12.0</version>
 </dependency>
 <dependency>
   <groupId>com.google.cloud</groupId>
@@ -32,12 +32,12 @@ 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:google-cloud-pubsublite:0.11.1'
+compile 'com.google.cloud:google-cloud-pubsublite:0.12.0'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-pubsublite" % "0.11.1"
+libraryDependencies += "com.google.cloud" % "google-cloud-pubsublite" % "0.12.0"
 ```
 
 ## Authentication