[2236] Remove obsolete comment

src/lib/util/threads/sync.cc

@@ -128,9 +128,6 @@ Mutex::~Mutex() {
 
 void
 Mutex::postLockAction() {
-    // This assertion would fail only in non-debugging mode, in which case
-    // this method wouldn't be called either, so we simply assert the
-    // condition.
     assert(impl_->locked_count == 0);
     ++impl_->locked_count;
 }