chore: regenerate README (#897)

This PR was generated using Autosynth. 🌈


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

```
2021-07-02 19:10:00,246 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigtable/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-02 19:10:01,800 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

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Author: yoshi-automation

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigtable.git",
-        "sha": "d2ca9c62f3fcb9c79c97ef8a73bad3a0e7555afc"
+        "sha": "ab628b66bd99ca5b61269e15a0a83e3afc40fbae"
       }
     },
     {

README.md

@@ -51,12 +51,12 @@ compile 'com.google.cloud:google-cloud-bigtable'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-bigtable:1.27.1'
+compile 'com.google.cloud:google-cloud-bigtable:1.27.2'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-bigtable" % "1.27.1"
+libraryDependencies += "com.google.cloud" % "google-cloud-bigtable" % "1.27.2"
 ```
 
 ## Authentication