Remove as_ptr member function from VRef

This reverts that part of commit
e5dfb3a4c0 since:

    * it's apparently not needed anymore
    * bad API for a type that also implements deref

helper_crates/vtable/src/lib.rs

@@ -264,12 +264,6 @@ impl<'a, T: ?Sized + VTableMeta> VRef<'a, T> {
         }
     }
 
-    /// Returns a raw pointer to the VRef's instance. This is primarily useful for comparisons.
-    /// The caller must ensure that the VRef outlives the pointer returned.
-    pub fn as_ptr(&self) -> *const u8 {
-        self.inner.ptr
-    }
-
     unsafe fn from_inner(inner: Inner) -> Self {
         Self { inner, phantom: PhantomData }
     }