Use double backticks in reStructuredText.

Author: deivse

docs/x509/verification.rst

@@ -112,14 +112,14 @@ the root of trust:
     .. versionadded:: 43.0.0
 
     .. versionchanged:: 44.0.0
-        Made `subjects` optional with the addition of custom extension policies.
+        Made ``subjects`` optional with the addition of custom extension policies.
 
     .. attribute:: subjects
 
         :type: list of :class:`~cryptography.x509.GeneralName` or None
 
         The subjects presented in the verified client's Subject Alternative Name
-        extension or `None` if the extension is not present.
+        extension or ``None`` if the extension is not present.
 
     .. attribute:: chain