fix: remove tests for null failure in volatile

Author: LuigiPiucco

tests/ui/precondition-checks/read_volatile.rs

@@ -1,7 +1,7 @@
 //@ run-fail
 //@ compile-flags: -Copt-level=3 -Cdebug-assertions=no -Zub-checks=yes
 //@ error-pattern: unsafe precondition(s) violated: ptr::read_volatile requires
-//@ revisions: null misaligned
+//@ revisions: misaligned
 
 #![allow(invalid_null_arguments)]
 
@@ -11,8 +11,6 @@ fn main() {
     let src = [0u16; 2];
     let src = src.as_ptr();
     unsafe {
-        #[cfg(null)]
-        ptr::read_volatile(ptr::null::<u8>());
         #[cfg(misaligned)]
         ptr::read_volatile(src.byte_add(1));
     }

tests/ui/precondition-checks/write_volatile.rs

@@ -1,18 +1,14 @@
 //@ run-fail
 //@ compile-flags: -Copt-level=3 -Cdebug-assertions=no -Zub-checks=yes
 //@ error-pattern: unsafe precondition(s) violated: ptr::write_volatile requires
-//@ revisions: null misaligned
-
-#![allow(invalid_null_arguments)]
+//@ revisions: misaligned
 
 use std::ptr;
 
 fn main() {
     let mut dst = [0u16; 2];
     let mut dst = dst.as_mut_ptr();
     unsafe {
-        #[cfg(null)]
-        ptr::write_volatile(ptr::null_mut::<u8>(), 1u8);
         #[cfg(misaligned)]
         ptr::write_volatile(dst.byte_add(1), 1u16);
     }