fix stale docstring in gc_sweep_page (JuliaLang#54743)

src/gc.c

@@ -1423,7 +1423,8 @@ STATIC_INLINE void gc_dump_page_utilization_data(void) JL_NOTSAFEPOINT
 
 int64_t buffered_pages = 0;
 
-// Returns pointer to terminal pointer of list rooted at *pfl.
+// Walks over a page, reconstruting the free lists if the page contains at least one live object. If not,
+// queues up the page for later decommit (i.e. through `madvise` on Unix).
 static void gc_sweep_page(gc_page_profiler_serializer_t *s, jl_gc_pool_t *p, jl_gc_page_stack_t *allocd, jl_gc_page_stack_t *buffered,
                           jl_gc_pagemeta_t *pg, int osize) JL_NOTSAFEPOINT
 {