chore: regenerate README (#500)

This PR was generated using Autosynth. 🌈


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

```
2021-07-29 19:54:04,762 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-mediatranslation/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-29 19:54:06,605 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/a1c7380b-6115-422e-8490-551b527529cf/targets

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

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-mediatranslation.git",
-        "sha": "64337c10e975c65764f2ea11aec8f65d7b253fc1"
+        "sha": "a9272d27c2e3921dd5e6831188b2f5eca08d383c"
       }
     },
     {