chore: regenerate README (#734)

This PR was generated using Autosynth. 🌈


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

```
2021-04-06 16:45:25,909 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigquerydatatransfer/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-06 16:45:27,203 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/e97137a5-3a22-4c7b-bdf3-364d27814002/targets

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

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigquerydatatransfer.git",
-        "sha": "c64078f821d1aa545466c2df360ed5320d73c8e9"
+        "sha": "98a9a1aa39872c888ab2927316dfc42b54a91d9b"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "063de45298fbdd88916018ba566c7ecd254b39ae"
+        "sha": "5b5bf6d519b2d658d9f2e483d9f6f3d0ba8ee6bc"
       }
     }
   ]

README.md

@@ -38,7 +38,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-bigquerydatatransfer</artifactId>
-  <version>1.2.4</version>
+  <version>1.2.5</version>
 </dependency>
 
 ```