docs: clarify peer id as Cidv1

Author: hacdias

src/routing/http-routing-v1.md

@@ -108,7 +108,8 @@ Each object in the `Providers` list is a *read provider record*.
 
 #### Path Parameters
 
-- `peer-id` is the [Peer ID](https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md) to fetch peer records for.
+- `peer-id` is the [Peer ID](https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md) to fetch peer records for,
+represented as a CIDv1 encoded with `libp2p-key` codec.
 
 #### Response Status Codes