gh-144289: Remove ENABLE_SPECIALIZATION_FT (gh-144290)

Now that the specializing interpreter works with free threading,
replace ENABLE_SPECIALIZATION_FT with ENABLE_SPECIALIZATION and
replace requires_specialization_ft with requires_specialization.

Also limit the uniquely referenced check to FOR_ITER_RANGE. It's not
necessary for FOR_ITER_GEN and would cause test_for_iter_gen to fail.

Modules/_opcode.c

@@ -423,9 +423,6 @@ _opcode_exec(PyObject *m) {
     if (PyModule_AddIntMacro(m, ENABLE_SPECIALIZATION) < 0) {
         return -1;
     }
-    if (PyModule_AddIntMacro(m, ENABLE_SPECIALIZATION_FT) < 0) {
-        return -1;
-    }
     return 0;
 }