chore: regenerate README (#869)

This PR was generated using Autosynth. 🌈


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

```
2021-06-07 18:54:02,051 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigtable/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-06-07 18:54:03,538 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/1ba9e346-f363-4a3a-870e-8f9f56e19599/targets

- [ ] To automatically regenerate this PR, check this box. (May take up to 24 hours.)

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigtable.git",
-        "sha": "f0ded00a69ccee27535c84f926f41e1256988f5c"
+        "sha": "ccb869cfc5f343ac5ecaec3b424498ce45b66fd1"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "8da7927493739fa36130360019ca21258242f73a"
+        "sha": "2430f8d90ed8a508e8422a3a7191e656d5a6bf53"
       }
     }
   ]

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>1.26.0</version>
+  <version>1.26.1</version>
 </dependency>
 
 ```