Replace the Mozilla logos with generic versions.

The Mozilla logo is replaced with the Hubs duck logo with white horizontal text.
The Spoke logo is replaced with the Spoke icon with white horizontal text.

src/ui/navigation/Footer.js

@@ -1,6 +1,6 @@
 import React, { Component } from "react";
 import { Link } from "react-router-dom";
-import mozillaLogo from "../../assets/mozilla-logo.png";
+import hubsLogo from "../../assets/hubs-logo.png";
 import styled from "styled-components";
 import configs from "../../configs";
 import { TERMS, PRIVACY } from "../../constants";
@@ -103,7 +103,7 @@ export default class Footer extends Component {
             {configs.isMoz() && (
               <NavListItem>
                 <a href="https://hubsfoundation.org" rel="noopener noreferrer">
-                  <img alt="Hubs" src={mozillaLogo} />
+                  <img alt="Hubs" src={hubsLogo} />
                 </a>
               </NavListItem>
             )}