SI-7329 duplicate default getters for specialized parameters.

The default getter is generated with @specialized annotation if the
type parameter corresponding to the type of the parameter is
specialized. Consequently specialize pass tries to generate overloads.

Rather than pruning overloads to exclude duplicates, let's notice
that default getter specialization is not needed at all:
  - it is executed outside the context of specialized method or class,
    so the annotation shouldn't make effect.
  - generic default getter is called even when calling specialized
    method:
    object V {
      @specialized def foo[@specialized B](b: B = (??? : B)) = {}
      foo[Int]()
    }
    gives:
      invokevirtual Method V$.foo$default$1:()Ljava/lang/Object;
      invokestatic (unboxToInt)
      invokevirtual Method V$.foo$mIc$sp:(I)V