doc: maintain only one list of MODP groups

There are two lists of MODP groups, one of which is redundant and does
not mark weak groups as deprecated. Remove said list and refer readers
to the first list instead.

Refs: #43986
Refs: #44588
PR-URL: #44644
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/crypto.md

@@ -4080,10 +4080,9 @@ added: v0.7.5
 * Returns: {DiffieHellmanGroup}
 
 Creates a predefined `DiffieHellmanGroup` key exchange object. The
-supported groups are: `'modp1'`, `'modp2'`, `'modp5'` (defined in
-[RFC 2412][], but see [Caveats][]) and `'modp14'`, `'modp15'`,
-`'modp16'`, `'modp17'`, `'modp18'` (defined in [RFC 3526][]). The
-returned object mimics the interface of objects created by
+supported groups are listed in the documentation for [`DiffieHellmanGroup`][].
+
+The returned object mimics the interface of objects created by
 [`crypto.createDiffieHellman()`][], but will not allow changing
 the keys (with [`diffieHellman.setPublicKey()`][], for example). The
 advantage of using this method is that the parties do not have to
@@ -6001,7 +6000,6 @@ See the [list of SSL OP Flags][] for details.
 [OpenSSL's SPKAC implementation]: https://www.openssl.org/docs/man1.1.0/apps/openssl-spkac.html
 [RFC 1421]: https://www.rfc-editor.org/rfc/rfc1421.txt
 [RFC 2409]: https://www.rfc-editor.org/rfc/rfc2409.txt
-[RFC 2412]: https://www.rfc-editor.org/rfc/rfc2412.txt
 [RFC 2818]: https://www.rfc-editor.org/rfc/rfc2818.txt
 [RFC 3526]: https://www.rfc-editor.org/rfc/rfc3526.txt
 [RFC 3610]: https://www.rfc-editor.org/rfc/rfc3610.txt
@@ -6012,6 +6010,7 @@ See the [list of SSL OP Flags][] for details.
 [Web Crypto API documentation]: webcrypto.md
 [`BN_is_prime_ex`]: https://www.openssl.org/docs/man1.1.1/man3/BN_is_prime_ex.html
 [`Buffer`]: buffer.md
+[`DiffieHellmanGroup`]: #class-diffiehellmangroup
 [`EVP_BytesToKey`]: https://www.openssl.org/docs/man1.1.0/crypto/EVP_BytesToKey.html
 [`KeyObject`]: #class-keyobject
 [`Sign`]: #class-sign