Update sbt to 1.3.8 (scala#81)

scala-steward · web-flow · commit b77e613ab558 · 2020-02-03T17:23:22.000-08:00
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.3.7
+sbt.version=1.3.8
