Update sbt to 1.12.6 (#96)

Co-authored-by: nmcb-scala-steward[bot] <157481287+nmcb-scala-steward[bot]@users.noreply.github.com>

Author: nmcb-scala-steward[bot]

project/build.properties

@@ -1 +1 @@
-sbt.version=1.12.5
+sbt.version=1.12.6