Fix Markdown formatting in README.

PiperOrigin-RevId: 461722304

README.md

@@ -1,4 +1,4 @@
-LevelDB is a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.**
+LevelDB is a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.
 
 > **This repository is receiving very limited maintenance. We will only review the following types of changes.**
 >