chore: regenerate README (#262)

This PR was generated using Autosynth. 🌈


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

```
2020-10-16 16:25:13,479 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-texttospeech/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working directory clean
2020-10-16 16:25:14,419 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/1c4becb4-2391-47ed-9c88-702a8b43ef62/targets

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

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

@@ -0,0 +1,18 @@
+{
+  "sources": [
+    {
+      "git": {
+        "name": ".",
+        "remote": "https://github.com/googleapis/java-texttospeech.git",
+        "sha": "d4ce2af0232ac85f28319aede37b6d9f9346f2a5"
+      }
+    },
+    {
+      "git": {
+        "name": "synthtool",
+        "remote": "https://github.com/googleapis/synthtool.git",
+        "sha": "5451633881133e5573cc271a18e73b18caca8b1b"
+      }
+    }
+  ]
+}

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>10.1.0</version>
+      <version>12.1.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -44,8 +44,6 @@ If you are using Maven without BOM, add this to your dependencies:
 
 ```
 
-[//]: # ({x-version-update-start:google-cloud-texttospeech:released})
-
 If you are using Gradle, add this to your dependencies
 ```Groovy
 compile 'com.google.cloud:google-cloud-texttospeech:1.2.1'
@@ -54,7 +52,6 @@ If you are using SBT, add this to your dependencies
 ```Scala
 libraryDependencies += "com.google.cloud" % "google-cloud-texttospeech" % "1.2.1"
 ```
-[//]: # ({x-version-update-end})
 
 ## Authentication