chore: regenerate README (#698)

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigtable.git",
-        "sha": "8b04cb945c0544a8af02eb88718d6f6fbd944e4d"
+        "sha": "ca1f5ed15e4de409ae00b5afa5357d65def04c51"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "86ed43d4f56e6404d068e62e497029018879c771"
+        "sha": "6d76df2138f8f841e5a5b9ac427f81def520c15f"
       }
     }
   ]

README.md

@@ -38,7 +38,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-bigtable</artifactId>
-  <version>1.21.2</version>
+  <version>1.21.3</version>
 </dependency>
 
 ```
@@ -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:1.21.2'
+compile 'com.google.cloud:google-cloud-bigtable:1.21.3'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-bigtable" % "1.21.2"
+libraryDependencies += "com.google.cloud" % "google-cloud-bigtable" % "1.21.3"
 ```
 
 ## Authentication