Bug 20581: (follow-up) Modify POD

As per:
https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=20581#c69

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>

Koha/Illrequest.pm

@@ -114,8 +114,8 @@ available for request.
 
     my $statusalias = $request->statusalias;
 
-Return a request's status alias, if one is defined, otherwise
-return implicit undef
+Returns a request's status alias, as a Koha::AuthorisedValue instance
+or implicit undef
 
 =cut