Merge pull request scala#4592 from xuwei-k/patch-2

fix README. 2.12.x branch require Java 8

Author: adriaanm

README.md

@@ -62,7 +62,7 @@ scala/
 
 ## Requirements
 
-You'll need a Java SDK (6 or newer), Apache Ant (version 1.8.0 or above), and curl (for `./pull-binary-libs.sh`).
+You'll need a Java SDK (8 or newer), Apache Ant (version 1.8.0 or above), and curl (for `./pull-binary-libs.sh`).
 
 ## Git Hygiene