disable tasty file checks for Scala 2.11 and Scala 2.12 users

[pjfanning]

The tasty file checks are useful for Scala 2.13 and Scala 3 users but you there is no compatibility between Scala 3 and Scala 2.11/2.12.

https://docs.scala-lang.org/scala3/guides/migration/compatibility-classpath.html

This will improve performance for Scala 2.11/2.12 users.

[pjfanning]

in 2.14.0-rc3