Fix test

Author: odersky

compiler/test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala

@@ -5,7 +5,7 @@ import dotty.tools.dotc.ast.tpd.TreeOps
 import dotty.tools.dotc.{Driver, Main}
 import dotty.tools.dotc.core.Comments.CommentsContext
 import dotty.tools.dotc.core.Contexts.Context
-import dotty.tools.dotc.core.Decorators.PreNamedString
+import dotty.tools.dotc.core.Decorators.{toTermName, toTypeName}
 import dotty.tools.dotc.core.Mode
 import dotty.tools.dotc.core.Names.Name
 import dotty.tools.dotc.interfaces.Diagnostic.ERROR