Use backend method to check if ML-DSA is supported

Signed-off-by: Facundo Tuesca <facundo.tuesca@trailofbits.com>

Author: facutuesca

docs/conf.py

@@ -51,8 +51,7 @@
 ]
 
 doctest_global_setup = """
-from cryptography.hazmat.bindings._rust import openssl as _rust_openssl
-SKIP_MLDSA = not _rust_openssl.CRYPTOGRAPHY_IS_AWSLC
+from cryptography.hazmat.backends.openssl.backend import backend as _backend
 """
 
 if spelling is not None:

docs/hazmat/primitives/asymmetric/mldsa.rst

@@ -12,7 +12,7 @@ Signing & Verification
 ~~~~~~~~~~~~~~~~~~~~~~~
 
 .. doctest::
-    :skipif: SKIP_MLDSA
+    :skipif: not _backend.mldsa_supported()
 
     >>> from cryptography.hazmat.primitives.asymmetric.mldsa import MlDsa65PrivateKey
     >>> private_key = MlDsa65PrivateKey.generate()
@@ -28,7 +28,7 @@ The context can be up to 255 bytes and is used to differentiate signatures in
 different contexts or protocols.
 
 .. doctest::
-    :skipif: SKIP_MLDSA
+    :skipif: not _backend.mldsa_supported()
 
     >>> from cryptography.hazmat.primitives.asymmetric.mldsa import MlDsa65PrivateKey
     >>> private_key = MlDsa65PrivateKey.generate()
@@ -69,7 +69,7 @@ Key interfaces
             not supported by the backend ``cryptography`` is using.
 
         .. doctest::
-            :skipif: SKIP_MLDSA
+            :skipif: not _backend.mldsa_supported()
 
             >>> from cryptography.hazmat.primitives.asymmetric import mldsa
             >>> private_key = mldsa.MlDsa65PrivateKey.generate()
@@ -158,7 +158,7 @@ Key interfaces
             not supported by the backend ``cryptography`` is using.
 
         .. doctest::
-            :skipif: SKIP_MLDSA
+            :skipif: not _backend.mldsa_supported()
 
             >>> from cryptography.hazmat.primitives import serialization
             >>> from cryptography.hazmat.primitives.asymmetric import mldsa