chore: regenerate README (#677)

This PR was generated using Autosynth. 🌈


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

```
2021-05-20 22:35:59,913 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-pubsub/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-05-20 22:36:01,248 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/08b33367-0f6b-4cac-b750-0709b6d70deb/targets

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-pubsub.git",
-        "sha": "6f6e341738e8b10a0a8c0a7441a087b6a8850543"
+        "sha": "28f8dd906f85b0f54beebb0fde786aabfc0fc42c"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "4f4b1b9b8d8b52f1e9e4a76165896debce5ab7f1"
+        "sha": "8eae0234a16b26c2ff616d305dbd9786c8b10a47"
       }
     }
   ]

README.md

@@ -53,12 +53,12 @@ compile 'com.google.cloud:google-cloud-pubsub'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-pubsub:1.112.5'
+compile 'com.google.cloud:google-cloud-pubsub:1.111.2'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-pubsub" % "1.112.5"
+libraryDependencies += "com.google.cloud" % "google-cloud-pubsub" % "1.111.2"
 ```
 
 ## Authentication