[Temporary] Bump Tasty version

Make sure that the full bootstrap still works when the reference
compiler uses a different Tasty version.

Author: smarter

compiler/src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -244,7 +244,7 @@ Standard Section: "Comments" Comment*
 object TastyFormat {
 
   final val header: Array[Int] = Array(0x5C, 0xA1, 0xAB, 0x1F)
-  val MajorVersion: Int = 13
+  val MajorVersion: Int = 14
   val MinorVersion: Int = 0
 
   /** Tags used to serialize names */