Update core/mem/doc.odin

core/mem/doc.odin

@@ -18,6 +18,7 @@ _main :: proc() {
 main :: proc() {
 	track: mem.Tracking_Allocator
 	mem.tracking_allocator_init(&track, context.allocator)
+	defer mem.tracking_allocator_destroy(&track)
 	context.allocator = mem.tracking_allocator(&track)
 
 	_main()
@@ -31,4 +32,4 @@ main :: proc() {
 }
 ```
 */
-package mem
+package mem