chore: regenerate README (#714)

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

```
2021-04-09 16:58:59,574 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigtable/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-04-09 16:59:00,970 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

@@ -4,14 +4,14 @@
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-        "sha": "15ebd39a120ac8306077340f039e5f50bcd17288"
+        "sha": "47e145210bc7506ad280e535e916dc023582681b"
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-        "sha": "705743e66f5c0b24a95f7f30619c9d3ef747b317"
+        "sha": "5b0e1592dd7d70b485e157ea4b3eb1704ecbd015"
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     }
   ]

README.md

@@ -8,6 +8,9 @@ Java idiomatic client for [Cloud Bigtable][product-docs].
 - [Product Documentation][product-docs]
 - [Client Library Documentation][javadocs]
 
+
+
+
 ## Quickstart
 
 If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file