chore: regenerate README (#817)

This PR was generated using Autosynth. 🌈


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

```
2021-05-11 01:23:33,729 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigquerydatatransfer/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-05-11 01:23:35,087 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/10038d90-c2ee-4ed4-8547-e7a081071481/targets

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Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigquerydatatransfer.git",
-        "sha": "f35fd175020af48d3b8a40e6944d4c0c47046bd4"
+        "sha": "a71020b5056ec3e42fe2b8cd08673d1bf9b01d81"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "06a8cd0ff7e81b05e6c503eab510ec622384caa7"
+        "sha": "6726988c677bb78385868bfc48dbfa2fe981d44a"
       }
     }
   ]

README.md

@@ -17,7 +17,7 @@ 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>20.2.0</version>
+      <version>20.3.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -38,25 +38,25 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-bigquerydatatransfer</artifactId>
-  <version>1.2.11</version>
+  <version>1.2.12</version>
 </dependency>
 
 ```
 
 If you are using Gradle 5.x or later, add this to your dependencies
 ```Groovy
-implementation platform('com.google.cloud:libraries-bom:20.2.0')
+implementation platform('com.google.cloud:libraries-bom:20.3.0')
 
 compile 'com.google.cloud:google-cloud-bigquerydatatransfer'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-bigquerydatatransfer:1.2.11'
+compile 'com.google.cloud:google-cloud-bigquerydatatransfer:1.2.12'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-bigquerydatatransfer" % "1.2.11"
+libraryDependencies += "com.google.cloud" % "google-cloud-bigquerydatatransfer" % "1.2.12"
 ```
 
 ## Authentication