doc: correct name of engine methods

Original Commit Message:
  ENGINE_METHOD_PKEY_METH and ENGINE_METHOD_PKEY_ASN1_METH are misspelled
  in the documentation, both should be ..._METHS.

  PR-URL: #5463
  Reviewed-By: Fedor Indutny <fedor@indutny.com>

Backport-Of: #5463
PR-URL: #11002
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/crypto.md

@@ -1516,8 +1516,8 @@ is a bit field taking one of or a mix of the following flags (defined in the
 * `ENGINE_METHOD_CIPHERS`
 * `ENGINE_METHOD_DIGESTS`
 * `ENGINE_METHOD_STORE`
-* `ENGINE_METHOD_PKEY_METH`
-* `ENGINE_METHOD_PKEY_ASN1_METH`
+* `ENGINE_METHOD_PKEY_METHS`
+* `ENGINE_METHOD_PKEY_ASN1_METHS`
 * `ENGINE_METHOD_ALL`
 * `ENGINE_METHOD_NONE`