fix(wot): cannot certify self

An identity should not be able to certify itself.

@librelois

pallets/duniter-wot/src/lib.rs

@@ -158,6 +158,9 @@ impl<T: Config<I>, I: 'static> pallet_certification::traits::IsCertAllowed<IdtyI
     for Pallet<T, I>
 {
     fn is_cert_allowed(issuer: IdtyIndex, receiver: IdtyIndex) -> bool {
+        if issuer == receiver {
+            return false;
+        }
         if let Some(issuer_data) = pallet_identity::Pallet::<T>::identity(issuer) {
             if issuer_data.status != IdtyStatus::Validated {
                 return false;