Update sbt to 1.2.8

scala-steward · scala-steward · commit b62de1c3f9e5 · 2019-07-08T19:48:08.000+02:00
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.1.4
+sbt.version=1.2.8
