Opaque another OpenSSL struct (#3025)

diff --git a/src/_cffi_src/openssl/x509.py b/src/_cffi_src/openssl/x509.py
index 99b565a..fe08b27 100644
--- a/src/_cffi_src/openssl/x509.py
+++ b/src/_cffi_src/openssl/x509.py
@@ -36,14 +36,7 @@
     ...;
 } X509_CINF;
 
-/* TODO: opaque X509_EXTENSION. Cryptography no longer depends on it being
-   non-opaque but pyOpenSSL needs a release where it doesn't depend on this */
-typedef struct {
-    ASN1_OBJECT *object;
-    ASN1_BOOLEAN critical;
-    ASN1_OCTET_STRING *value;
-} X509_EXTENSION;
-
+typedef ... X509_EXTENSION;
 typedef ... X509_EXTENSIONS;
 typedef ... X509_REQ_INFO;