Fixup Atomic*::from_ptr safety docs

Author: WaffleLapkin

library/core/src/sync/atomic.rs

@@ -357,6 +357,8 @@ impl AtomicBool {
     ///     duration of lifetime `'a`. Most use cases should be able to follow this guideline.
     ///   * This requirement is also trivially satisfied if all accesses (atomic or not) are done
     ///     from the same thread.
+    /// * This method must not be used to perform overlapping or mixed-size atomic
+    ///   accesses, as these are not supported by the memory model.
     ///
     /// [valid]: crate::ptr#safety
     #[stable(feature = "atomic_from_ptr", since = "CURRENT_RUSTC_VERSION")]
@@ -1159,7 +1161,7 @@ impl<T> AtomicPtr<T> {
     ///     duration of lifetime `'a`. Most use cases should be able to follow this guideline.
     ///   * This requirement is also trivially satisfied if all accesses (atomic or not) are done
     ///     from the same thread.
-    /// * This method should not be used to create overlapping or mixed-size atomic accesses, as
+    /// * This method must not be used to perform overlapping or mixed-size atomic accesses, as
     ///   these are not supported by the memory model.
     ///
     /// [valid]: crate::ptr#safety
@@ -2142,7 +2144,7 @@ macro_rules! atomic_int {
             ///     this guideline.
             ///   * This requirement is also trivially satisfied if all accesses (atomic or not) are
             ///     done from the same thread.
-            /// * This method should not be used to create overlapping or mixed-size atomic
+            /// * This method must not be used to perform overlapping or mixed-size atomic
             ///   accesses, as these are not supported by the memory model.
             ///
             /// [valid]: crate::ptr#safety