chore: regenerate README (#509)

This PR was generated using Autosynth. 🌈


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

```
2021-08-31 22:14:07,566 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dns/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-08-31 22:14:08,716 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/99440e05-959e-4f9f-95c4-eaca45667c29/targets

- [ ] To automatically regenerate this PR, check this box. (May take up to 24 hours.)
- [ ] 
feat!: java8 migration

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dns.git",
-        "sha": "87db9682770759e1ec48001c006886233a19394d"
+        "sha": "2b9ba2736e4cb813b6f4eee2df64d6a9aac4327a"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "8032ab5a32471d85ece8fc261df16cc40fbfa4fb"
+        "sha": "9a238a0623879c3de129a376c6085d4a862f6eb9"
       }
     }
   ]

README.md

@@ -19,7 +19,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>21.0.0</version>
+      <version>22.0.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -41,28 +41,28 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-dns</artifactId>
-  <version>1.2.6</version>
+  <version>1.2.8</version>
 </dependency>
 
 ```
 
 If you are using Gradle 5.x or later, add this to your dependencies
 
 ```Groovy
-implementation platform('com.google.cloud:libraries-bom:21.0.0')
+implementation platform('com.google.cloud:libraries-bom:22.0.0')
 
-compile 'com.google.cloud:google-cloud-dns'
+implementation 'com.google.cloud:google-cloud-dns'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 
 ```Groovy
-compile 'com.google.cloud:google-cloud-dns:1.2.7'
+implementation 'com.google.cloud:google-cloud-dns:1.2.8'
 ```
 
 If you are using SBT, add this to your dependencies
 
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-dns" % "1.2.7"
+libraryDependencies += "com.google.cloud" % "google-cloud-dns" % "1.2.8"
 ```
 
 ## Authentication