chore: regenerate README (#694)

This PR was generated using Autosynth. 🌈


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

```
2020-12-10 00:01:20,093 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-spanner/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2020-12-10 00:01:20,993 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/103d8fd6-5614-472a-93cf-ae1bda29da9c/targets

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

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-spanner.git",
-        "sha": "7a51606e49dfa4816dcbfd23d133e66414f3e52c"
+        "sha": "6d45a465f77fef4d9d9d404fd6382d3e259415d5"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "5d11bd2888c38ce1fb6fa6bf25494a4219a73928"
+        "sha": "352f25621c28d2fa0784984ea0ed5ea697aa1525"
       }
     }
   ]

README.md

@@ -281,6 +281,8 @@ Java 8 OSX | [![Kokoro CI][kokoro-badge-image-3]][kokoro-badge-link-3]
 Java 8 Windows | [![Kokoro CI][kokoro-badge-image-4]][kokoro-badge-link-4]
 Java 11 | [![Kokoro CI][kokoro-badge-image-5]][kokoro-badge-link-5]
 
+Java is a registered trademark of Oracle and/or its affiliates.
+
 [product-docs]: https://cloud.google.com/spanner/docs/
 [javadocs]: https://googleapis.dev/java/google-cloud-spanner/latest/
 [kokoro-badge-image-1]: http://storage.googleapis.com/cloud-devrel-public/java/badges/java-spanner/java7.svg