Use our cryptography-specific warning class (#4493)

diff --git a/src/cryptography/hazmat/bindings/openssl/binding.py b/src/cryptography/hazmat/bindings/openssl/binding.py
index d52619d..0824ea8 100644
--- a/src/cryptography/hazmat/bindings/openssl/binding.py
+++ b/src/cryptography/hazmat/bindings/openssl/binding.py
@@ -160,7 +160,7 @@
             "OpenSSL version 1.0.1 is no longer supported by the OpenSSL "
             "project, please upgrade. A future version of cryptography will "
             "drop support for it.",
-            DeprecationWarning
+            utils.CryptographyDeprecationWarning
         )