chore: regenerate README (#521)

This PR was generated using Autosynth. 🌈


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

```
2021-01-25 17:40:08,181 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-asset/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-01-25 17:40:09,374 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/d3dcdec0-08d7-4ea2-87f6-6e34eb26fd66/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-asset.git",
-        "sha": "f5e20bb6a44e78b4949ad802c86109fc885c943c"
+        "sha": "e28e0851a1f2d6c95a6da236554c51ebcd606d34"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "67f09bf301083798e7220137723222eb00b8f88a"
+        "sha": "b259489b06b25f399768b74b8baa943991f38ea7"
       }
     }
   ]

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:16.2.1')
+implementation platform('com.google.cloud:libraries-bom:16.3.0')
 
 compile 'com.google.cloud:google-cloud-asset'
 ```