Update README.md (#3910)

Author: mandlil

README.md

@@ -55,7 +55,7 @@ Cream Sandwich).
 The [Java demo](https://libphonenumber.appspot.com/) is updated with a slight
 delay after the GitHub release.
 
-Last demo update: v9.0.12.
+Last demo update: v9.0.13.
 
 Note: Even though the library (main branch/[maven release](https://repo1.maven.org/maven2/com/googlecode/libphonenumber/libphonenumber/8.12.56/))
 is at v8.12.57, because of some deployment issues, we were unable to update the