Hardcode scala.version to 2.11 in flink-quickstart-scala

Currently, the scala.binary.version of the Scala Quickstart is derived from the scala.binary.version of Flink at the time when the Quickstart is built. This means that whatever Scala version is active when we push the Quickstart takes precedence. Currently, when deploying SNAPSHOT versions we deploy 2.10 first, then 2.11, i.e. the 1.4-SNAPSHOT Scala Quickstart has Scala version 2.11. The release script deploys first 2.11 and then 2.10, meaning the final 1.4.0 Scala Quickstart would have 2.10.

Simply fixing it to the latest supported (by Flink) will circumvent that issue and users can easily change the Scala version in the Quickstart.