doc: use duniter repo

docs/dev/upgrade-substrate.md

@@ -21,7 +21,7 @@ ParityTech frequently releases upgrades of the polkadot-sdk. For each upgrade, D
 
 ## 3. Upgrade Dependencies
 
-Ensure that the dependencies for [Arkwork](https://github.com/duniter/arkworks-substrate) and [ring-vrf bandersnatch-vrfs](https://github.com/bgallois/ring-vrf/blob/master/bandersnatch_vrfs/) are exclusively only depend on the duniter-polkadot-sdk. When upgrading these repositories, make sure to cherry-pick the "use duniter polkadot-sdk" commit.
+Ensure that the dependencies for [Arkwork](https://github.com/duniter/arkworks-substrate) and [ring-vrf bandersnatch-vrfs](https://github.com/duniter/ring-vrf/) only depend on the duniter-polkadot-sdk. When upgrading these repositories, make sure to cherry-pick the "use duniter polkadot-sdk" commit.
 
 ## 4. Upgrade repository