chore: regenerate README (#922)

This PR was generated using Autosynth. 🌈


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

```
2021-07-26 14:43:45,947 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigtable/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-26 14:43:47,224 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

Full log will be available here:
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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-bigtable.git",
-        "sha": "68d80f3a6182714d746f9c5b2ae384f364525dd9"
+        "sha": "887d6c6661e27643e5f386a7aa6041bb97084c0d"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "52e4e46eff2a0b70e3ff5506a02929d089d077d4"
+        "sha": "dd05f9d12f134871c9e45282349c9856fbebecdd"
       }
     }
   ]

README.md

@@ -17,7 +17,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>20.8.0</version>
+      <version>20.9.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -45,7 +45,7 @@ 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:20.8.0')
+implementation platform('com.google.cloud:libraries-bom:20.9.0')
 
 compile 'com.google.cloud:google-cloud-bigtable'
 ```
@@ -458,8 +458,7 @@ see [Assign CPU Resources to Containers](https://kubernetes.io/docs/tasks/config
 
 ## Samples
 
-Samples are in the [`samples/`](https://github.com/googleapis/java-bigtable/tree/master/samples) directory. The samples' `README.md`
-has instructions for running the samples.
+Samples are in the [`samples/`](https://github.com/googleapis/java-bigtable/tree/master/samples) directory.
 
 | Sample                      | Source Code                       | Try it |
 | --------------------------- | --------------------------------- | ------ |