NFC: remove unused gc_get_stack_ptr function (#55234)

Author: d-netto

src/gc.c

@@ -218,12 +218,6 @@ arraylist_t finalizer_list_marked;
 arraylist_t to_finalize;
 JL_DLLEXPORT _Atomic(int) jl_gc_have_pending_finalizers = 0;
 
-
-NOINLINE uintptr_t gc_get_stack_ptr(void)
-{
-    return (uintptr_t)jl_get_frame_addr();
-}
-
 void jl_gc_wait_for_the_world(jl_ptls_t* gc_all_tls_states, int gc_n_threads);
 
 // malloc wrappers, aligned allocation

src/gc.h

@@ -549,8 +549,6 @@ STATIC_INLINE void *gc_ptr_clear_tag(void *v, uintptr_t mask) JL_NOTSAFEPOINT
     return (void*)(((uintptr_t)v) & ~mask);
 }
 
-NOINLINE uintptr_t gc_get_stack_ptr(void);
-
 FORCE_INLINE void gc_big_object_unlink(const bigval_t *node) JL_NOTSAFEPOINT
 {
     assert(node != oldest_generation_of_bigvals);