chore: regenerate README (#272)

This PR was generated using Autosynth. 🌈


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

```
2020-10-16 00:17:16,783 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-billingbudgets/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working directory clean
2020-10-16 00:17:17,745 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/464ca364-c066-4a41-b1fe-dc270e4c76ce/targets

- [ ] To automatically regenerate this PR, check this box.

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-billingbudgets.git",
-        "sha": "0c1e2fc22f75d777bc5b249e172cb62cda43be5a"
+        "sha": "d58d9bc9c57183b50c325439245b0c8f5592bb69"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "27e0e916cbfdb3d5ff6639b686cc04f78a0b0386"
+        "sha": "7c5370937dd9ba9dcf9cd7d2af880a58b389b4f1"
       }
     }
   ]

README.md

@@ -20,7 +20,7 @@ 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>12.0.0</version>
+      <version>12.1.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>