Update Scala 2.13.15

Author: horothesun

src/main/g8/Main.scala

@@ -1,5 +1,5 @@
 $if(use_scala_3.truthy)$//> using scala 3.5.1
-$else$//> using scala 2.13.14
+$else$//> using scala 2.13.15
 $endif$
 $if(use_scala_native.truthy)$//> using platform native
 //> using nativeVersion 0.4.17