Allow Predicate Nodes To Be IRI Nodes Only
Allow Predicate Nodes To Be IRI Nodes Only

 - Previously, predicate nodes were allowed to be blank
 - Now, every predicate node will be of type IRI

Signed-off-by: RishabhBhatnagar <3f14ca5460db5da76f7a0004ecf5e8084affa295@gmail.com>

spdx/gordf