standard: Define PASSWORD_DEFAULT in terms of PASSWORD_BCRYPT (#24078)

Instead of copying the constant’s value, we can just refer to the constant,
making the stub more self-explanatory.

Author: TimWolla

ext/standard/password.stub.php

@@ -2,7 +2,6 @@
 
 /** @generate-class-entries */
 
-const PASSWORD_DEFAULT = "2y";
 const PASSWORD_BCRYPT = "2y";
 /**
  * @var int
@@ -30,3 +29,6 @@
  */
 const PASSWORD_ARGON2_DEFAULT_THREADS = UNKNOWN;
 #endif
+
+/** @var string */
+const PASSWORD_DEFAULT = PASSWORD_BCRYPT;