Update MIRI compiletests

Author: scottmcm

src/tools/miri/tests/fail/dangling_pointers/null_pointer_write_zst.rs

@@ -7,5 +7,5 @@ fn main() {
     // Also not assigning directly as that's array initialization, not assignment.
     let zst_val = [1u8; 0];
     unsafe { std::ptr::null_mut::<[u8; 0]>().write(zst_val) };
-    //~^ERROR: memory access failed: null pointer is a dangling pointer
+    //~^ERROR: dereferencing pointer failed: null pointer is a dangling pointer
 }

src/tools/miri/tests/fail/dangling_pointers/null_pointer_write_zst.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: memory access failed: null pointer is a dangling pointer (it has no provenance)
+error: Undefined Behavior: dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
   --> $DIR/null_pointer_write_zst.rs:LL:CC
    |
 LL |     unsafe { std::ptr::null_mut::<[u8; 0]>().write(zst_val) };
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: null pointer is a dangling pointer (it has no provenance)
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereferencing pointer failed: null pointer is a dangling pointer (it has no provenance)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information