Use 'over 2' for bullet lists.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3117)
diff --git a/doc/man3/RSA_generate_key.pod b/doc/man3/RSA_generate_key.pod
index 24e05bd..e51c0b1 100644
--- a/doc/man3/RSA_generate_key.pod
+++ b/doc/man3/RSA_generate_key.pod
@@ -32,7 +32,7 @@
 will be called as follows using the BN_GENCB_call() function
 described on the L<BN_generate_prime(3)> page.
 
-=over 4
+=over 2
 
 =item *