chore: regenerate README (#295)

This PR was generated using Autosynth. 🌈


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

```
2020-11-05 23:13:54,719 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-recaptchaenterprise/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working directory clean
2020-11-05 23:13:55,629 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/5cf324e2-9ab4-48b5-93af-ef0ef037f8c6/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-recaptchaenterprise.git",
-        "sha": "185e8e85f5c093e1c3bb04c63c29c826a09657de"
+        "sha": "412045f9f77b8bf192c580f6937c8e70b39c72c7"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "ba9918cd22874245b55734f57470c719b577e591"
+        "sha": "2c8aecedd55b0480fb4e123b6e07fa5b12953862"
       }
     }
   ]

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>14.4.1</version>
+      <version>15.0.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>