Remove unsized enum test

This was already tested (at least) by src/test/ui/unsized/unsized-enum2.rs

src/test/ui/issues/issue-17025.rs

@@ -1,13 +0,0 @@
-// ignore-test the unsized enum no longer compiles
-
-enum A {
-    B(char),
-    C([Box<A>]),
-}
-
-fn c(c:char) {
-    A::B(c);
-    //~^ ERROR cannot move a value of type A: the size of A cannot be statically determined
-}
-
-pub fn main() {}