Update sbt to 1.4.6 (#420)

scala-steward · web-flow · commit c057644a9200 · 2020-12-29T20:50:28.000+09:00
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.4.5
+sbt.version=1.4.6
