MAYBE_UNUSED should just suffice

This reverts commit c355fa72d4.

array.c

@@ -46,12 +46,14 @@ VALUE rb_cArray;
 #define ARY_MAX_SIZE (LONG_MAX / (int)sizeof(VALUE))
 #define SMALL_ARRAY_LEN 16
 
+RBIMPL_ATTR_MAYBE_UNUSED()
 static int
 should_be_T_ARRAY(VALUE ary)
 {
     return RB_TYPE_P(ary, T_ARRAY);
 }
 
+RBIMPL_ATTR_MAYBE_UNUSED()
 static int
 should_not_be_shared_and_embedded(VALUE ary)
 {
@@ -9100,11 +9102,6 @@ rb_ary_deconstruct(VALUE ary)
 void
 Init_Array(void)
 {
-    if (should_be_T_ARRAY(Qnil)) {
-        should_not_be_shared_and_embedded(Qnil);
-        UNREACHABLE;
-    }
-
 #undef rb_intern
 #define rb_intern(str) rb_intern_const(str)