rsa: document deprecated RSA command line apps

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11063)
diff --git a/doc/man1/openssl-genrsa.pod.in b/doc/man1/openssl-genrsa.pod.in
index ed26433..348f8cb 100644
--- a/doc/man1/openssl-genrsa.pod.in
+++ b/doc/man1/openssl-genrsa.pod.in
@@ -36,6 +36,9 @@
 
 =head1 DESCRIPTION
 
+This command has been deprecated.
+The L<openssl-genpkey(1)> command should be used instead.
+
 This command generates an RSA private key.
 
 =head1 OPTIONS
@@ -106,8 +109,13 @@
 =head1 SEE ALSO
 
 L<openssl(1)>,
+L<openssl-genpkey(1)>,
 L<openssl-gendsa(1)>
 
+=head1 HISTORY
+
+This command was deprecated in OpenSSL 3.0.
+
 =head1 COPYRIGHT
 
 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.