Simplify OCSP no check serialization (#4444)

diff --git a/src/_cffi_src/openssl/asn1.py b/src/_cffi_src/openssl/asn1.py
index 51acf10..82bf797 100644
--- a/src/_cffi_src/openssl/asn1.py
+++ b/src/_cffi_src/openssl/asn1.py
@@ -30,6 +30,7 @@
 typedef ... ASN1_TYPE;
 typedef ... ASN1_GENERALIZEDTIME;
 typedef ... ASN1_ENUMERATED;
+typedef ... ASN1_NULL;
 
 static const int V_ASN1_GENERALIZEDTIME;
 
@@ -97,6 +98,8 @@
 
 int i2d_ASN1_TYPE(ASN1_TYPE *, unsigned char **);
 ASN1_TYPE *d2i_ASN1_TYPE(ASN1_TYPE **, const unsigned char **, long);
+
+ASN1_NULL *ASN1_NULL_new(void);
 """
 
 CUSTOMIZATIONS = """
diff --git a/src/cryptography/hazmat/backends/openssl/encode_asn1.py b/src/cryptography/hazmat/backends/openssl/encode_asn1.py
index a2c7ed7..896ea05 100644
--- a/src/cryptography/hazmat/backends/openssl/encode_asn1.py
+++ b/src/cryptography/hazmat/backends/openssl/encode_asn1.py
@@ -245,11 +245,8 @@
 
 
 def _encode_ocsp_nocheck(backend, ext):
-    """
-    The OCSP No Check extension is defined as a null ASN.1 value embedded in
-    an ASN.1 string.
-    """
-    return _encode_asn1_str_gc(backend, b"\x05\x00", 2)
+    # Doesn't need to be GC'd
+    return backend._lib.ASN1_NULL_new()
 
 
 def _encode_key_usage(backend, key_usage):