Remove unused attr on backend (pyca#10285)

src/cryptography/hazmat/backends/openssl/backend.py

@@ -80,18 +80,6 @@ class Backend:
 
     name = "openssl"
 
-    # FIPS has opinions about acceptable algorithms and key sizes, but the
-    # disallowed algorithms are still present in OpenSSL. They just error if
-    # you try to use them. To avoid that we allowlist the algorithms in
-    # FIPS 140-3. This isn't ideal, but FIPS 140-3 is trash so here we are.
-    _fips_aead: typing.ClassVar[set[bytes]] = {
-        b"aes-128-ccm",
-        b"aes-192-ccm",
-        b"aes-256-ccm",
-        b"aes-128-gcm",
-        b"aes-192-gcm",
-        b"aes-256-gcm",
-    }
     # TripleDES encryption is disallowed/deprecated throughout 2023 in
     # FIPS 140-3. To keep it simple we denylist any use of TripleDES (TDEA).
     _fips_ciphers = (AES,)