cs: small memory-accounting simplification

Remove an unneeded accounting hook.

racket/src/cs/rumble/memory.ss

@@ -189,10 +189,6 @@
 
 ;; ----------------------------------------
 
-;; Any value wrapped as `strongly-reachable-for-accounting` will
-;; be `cons`ed instead of `weak-cons`ed for accounting purposes
-(define-record-type strongly-reachable-for-accounting (fields content))
-
 (define (weaken-accounting-roots roots)
   (let loop ([roots roots])
     (cond
@@ -202,8 +198,6 @@
              [rest (loop (cdr roots))])
          (cond
            [(thread? root) (cons root rest)]
-           [(strongly-reachable-for-accounting? root)
-            (cons (strongly-reachable-for-accounting-content root) rest)]
            [else
             (weak-cons root rest)]))])))
 

racket/src/cs/rumble/place.ss

@@ -94,9 +94,8 @@
                      (finish-proc result)))))
   ;; Must be called within an engine, used for memory accounting:
   (define (current-place-roots)
-    (make-strongly-reachable-for-accounting
-     (list (place-registers)
-           (current-engine-thread-cell-values))))]
+    (list (place-registers)
+          (current-engine-thread-cell-values)))]
  [else
   (define (place-enabled?) #f)
   (define (fork-place thunk finish-proc) #f)