Try to clarify destructor not being run scenario.

This is being discussed in https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Guarantees.20around.20Drop.20.28.2390752.29.

Author: nbdd0121

src/destructors.md

@@ -345,10 +345,14 @@ let x = (&temp()).use_temp();  // ERROR
 
 ## Not running destructors
 
-Not running destructors in Rust is safe even if it has a type that isn't
-`'static`. [`std::mem::ManuallyDrop`] provides a wrapper to prevent a
+[`std::mem::forget`] can be used to prevent the destructor of a variable from being run,
+and [`std::mem::ManuallyDrop`] provides a wrapper to prevent a
 variable or field from being dropped automatically.
 
+> Note: Preventing a destructor from being run via `forget` or other means is safe in Rust
+> even if it has a type that isn't `'static`. This means that publicly exposed APIs cannot
+> rely on destructor being run for soundness.
+
 [Assignment]: expressions/operator-expr.md#assignment-expressions
 [binding modes]: patterns.md#binding-modes
 [closure]: types/closure.md
@@ -395,4 +399,5 @@ variable or field from being dropped automatically.
 
 [`<T as std::ops::Drop>::drop`]: ../std/ops/trait.Drop.html#tymethod.drop
 [`std::ptr::drop_in_place`]: ../std/ptr/fn.drop_in_place.html
+[`std::mem::forget`]: ../std/mem/fn.forget.html
 [`std::mem::ManuallyDrop`]: ../std/mem/struct.ManuallyDrop.html