Fix deprecation policy link in CONTRIBUTING.md (Qiskit#11276)

* Fix deprecation policy link

* Update CONTRIBUTING.md

Co-authored-by: Eric Arellano <[email protected]>

---------

Co-authored-by: Eric Arellano <[email protected]>

Author: TsafrirA

CONTRIBUTING.md

@@ -651,7 +651,7 @@ def test_method2(self):
    self.assertEqual(result, <expected>)
 ```
 
-`test_method1_deprecated` can be removed after `Obj.method1` is removed (following the [Qiskit Deprecation Policy](https://qiskit.org/documentation/contributing_to_qiskit.html#deprecation-policy)).
+`test_method1_deprecated` can be removed after `Obj.method1` is removed (following the [Qiskit Deprecation Policy](./DEPRECATION.md)).
 
 ## Using dependencies