Update ipfs-http-client (for node >= 14)

Updates the client library and API usage to work with the latest
version, and more importantly, with current node.js LTS.

lib/contracts/base.js

@@ -14,15 +14,6 @@ class Base {
     return this.contract.address;
   }
 
-  get ipfs () {
-    if (!this._ipfsAPI) { throw new Error('IPFS API not configured; please set an ipfs instance'); }
-    return this._ipfsAPI;
-  }
-
-  set ipfs (ipfsAPI) {
-    this._ipfsAPI = ipfsAPI;
-  }
-
   on (type, callback) {
     return this.contract.on(type, callback);
   }