chore: regenerate README (#362)

This PR was generated using Autosynth. 🌈


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

```
2021-01-13 18:39:59,593 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-errorreporting/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-01-13 18:40:00,479 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

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https://source.cloud.google.com/results/invocations/93b1b23d-27a2-4a7a-8801-a3c0aff7ba10/targets

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Author: yoshi-automation

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-errorreporting.git",
-        "sha": "e568efe1f5490d250bad4f6480ee3fc56780892d"
+        "sha": "6188c8fd86808e720cd5770fcb919d16e9b0eee4"
       }
     },
     {

README.md

@@ -60,7 +60,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-errorreporting</artifactId>
-  <version>0.120.11-beta</version>
+  <version>0.120.12-beta</version>
 </dependency>
 
 ```