Make all leaks safe in language reference

Since it was determined that no leaks were unsafe, some of the documentation is still not clear about this. Here's one example.

src/doc/reference.md

@@ -1038,7 +1038,7 @@ be undesired.
 
 * Deadlocks
 * Reading data from private fields (`std::repr`)
-* Leaks due to reference count cycles, even in the global heap
+* Leaks of memory and other resources
 * Exiting without calling destructors
 * Sending signals
 * Accessing/modifying the file system