chore: regenerate README (#479)

This PR was generated using Autosynth. 🌈


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

```
2021-04-12 14:26:45,555 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-speech/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-12 14:26:46,853 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/a8148fae-cdd7-4aee-a286-496839c4d46c/targets

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

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-speech.git",
-        "sha": "f5f5d536e1d9cea52287d50234285ca34c0cdc26"
+        "sha": "1d040df3100dced0bd05900e524d830227937079"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "bb854b6c048619e3be4e8b8ce8ed10aa74ea78ef"
+        "sha": "0a071b3460344886297a304253bf924aa68ddb7e"
       }
     }
   ]

README.md

@@ -46,7 +46,7 @@ If you are using Maven without BOM, add this to your dependencies:
 
 If you are using Gradle 5.x or later, add this to your dependencies
 ```Groovy
-implementation platform('com.google.cloud:libraries-bom:19.2.1')
+implementation platform('com.google.cloud:libraries-bom:20.0.0')
 
 compile 'com.google.cloud:google-cloud-speech'
 ```