[test] Delete ChiselFreeSpec

Remove the non-load bearing ChiselFreeSpec.  Developers should use
Scalatest traits directly for their tests to make them more
self-contained.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

src/test/scala-2/chiselTests/ChiselSpec.scala

@@ -132,9 +132,6 @@ trait FileCheck extends BeforeAndAfterEachTestData { this: Suite =>
   }
 }
 
-/** Spec base class for BDD-style testers. */
-abstract class ChiselFreeSpec extends AnyFreeSpec with Matchers
-
 /** Spec base class for BDD-style testers. */
 abstract class ChiselFunSpec extends AnyFunSpec with Matchers