Remove unused rb_size_pool_slot_size

gc.c

@@ -2693,12 +2693,6 @@ size_pool_slot_size(unsigned char pool_id)
     return slot_size;
 }
 
-size_t
-rb_size_pool_slot_size(unsigned char pool_id)
-{
-    return size_pool_slot_size(pool_id);
-}
-
 bool
 rb_gc_size_allocatable_p(size_t size)
 {
@@ -2712,7 +2706,7 @@ rb_gc_size_pool_sizes(void)
 {
     if (size_pool_sizes[0] == 0) {
         for (unsigned char i = 0; i < SIZE_POOL_COUNT; i++) {
-            size_pool_sizes[i] = rb_size_pool_slot_size(i);
+            size_pool_sizes[i] = size_pool_slot_size(i);
         }
     }
 

internal/gc.h

@@ -119,8 +119,6 @@ int ruby_get_stack_grow_direction(volatile VALUE *addr);
 const char *rb_obj_info(VALUE obj);
 const char *rb_raw_obj_info(char *const buff, const size_t buff_size, VALUE obj);
 
-size_t rb_size_pool_slot_size(unsigned char pool_id);
-
 struct rb_execution_context_struct; /* in vm_core.h */
 struct rb_objspace; /* in vm_core.h */