Revert "Try to use Arbitrary"

This reverts commit 16f40c7.

library/core/src/ptr/alignment.rs

@@ -388,13 +388,6 @@ enum AlignmentEnum {
 mod verify {
     use super::*;
 
-    impl kani::Arbitrary for Alignment {
-        fn any() -> Self {
-            let align = kani::any_where(|a: &usize| a.is_power_of_two());
-            unsafe { mem::transmute::<usize, Alignment>(align) }
-        }
-    }
-
     // pub const fn of<T>() -> Self
     #[kani::proof]
     pub fn check_of_i32() {
@@ -430,8 +423,10 @@ mod verify {
     // pub const fn as_nonzero(self) -> NonZero<usize>
     #[kani::proof_for_contract(Alignment::as_nonzero)]
     pub fn check_as_nonzero() {
-        let alignment = kani::any::<Alignment>();
-        let _ = alignment.as_nonzero();
+        let a = kani::any::<usize>();
+        if let Some(alignment) = Alignment::new(a) {
+            let _ = alignment.as_nonzero();
+        }
     }
 
     // pub const fn log2(self) -> u32