chore: regenerate README (#401)

This PR was generated using Autosynth. 🌈


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

```
2021-06-07 22:37:45,872 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-aiplatform/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-06-07 22:37:47,204 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/2424478c-0089-4990-b2e1-5756a5459fcf/targets

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Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-aiplatform.git",
-        "sha": "545e0eaa13790872459b46c2e8e0702174401159"
+        "sha": "0d30f840fa9ab7215ea6e58e4f6b8fc8bdde8fd2"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "c3e41da0fa256ad7f6b4bc76b9d069dedecdfef4"
+        "sha": "2430f8d90ed8a508e8422a3a7191e656d5a6bf53"
       }
     }
   ]

README.md

@@ -37,7 +37,7 @@ 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:20.5.0')
+implementation platform('com.google.cloud:libraries-bom:20.6.0')
 
 compile 'com.google.cloud:google-cloud-aiplatform'
 ```