Document the recursive option

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4336)

doc/man1/storeutl.pod

diff --git a/doc/man1/storeutl.pod b/doc/man1/storeutl.pod
index 2792a55..1f72966 100644
--- a/doc/man1/storeutl.pod
+++ b/doc/man1/storeutl.pod
@@ -13,6 +13,7 @@
 [B<-passin arg>]
 [B<-text arg>]
 [B<-engine id>]
+[B<-r>]
 B<uri> ...
 
 =head1 DESCRIPTION
@@ -54,6 +55,10 @@
 thus initialising it if needed.
 The engine will then be set as the default for all available algorithms.
 
+=item B<-r>
+
+Fetch objects recursively when possible.
+
 =back
 
 =head1 SEE ALSO