Bump internal Scala version to 3.3.7 (#3906)

Author: Gedochao

project/deps/package.mill.scala

@@ -10,7 +10,7 @@ object Scala {
   def scala212         = "2.12.20"
   def scala213         = "2.13.17"
   def scala3LtsPrefix  = "3.3"                  // used for the LTS version tags
-  def scala3Lts        = s"$scala3LtsPrefix.6"  // the LTS version currently used in the build
+  def scala3Lts        = s"$scala3LtsPrefix.7"  // the LTS version currently used in the build
   def runnerScala3     = scala3Lts
   def scala3NextPrefix = "3.7"
   def scala3Next       = s"$scala3NextPrefix.3" // the newest/next version of Scala