Update dependency scala to v2.12.15

Author: renovate-bot

src/sbt-test/sbt-sourcegraph/basic/build.sbt

@@ -4,7 +4,7 @@ import java.nio.file.Files
 
 inThisBuild(
   List(
-    scalaVersion := "2.12.14",
+    scalaVersion := "2.12.15",
     organization := "com.example"
   )
 )