Remove obsolete attributes from crate model

These may have existed at some point, but these fields are no longer sent by the backend, so there is no point in us still handling them

Author: Turbo87

app/components/crate-sidebar.hbs

@@ -46,20 +46,6 @@
         />
       {{/if}}
 
-      {{#if @crate.wiki}}
-        <CrateSidebar::Link
-          @title="Wiki"
-          @url={{@crate.wiki}}
-        />
-      {{/if}}
-
-      {{#if @crate.mailing_list}}
-        <CrateSidebar::Link
-          @title="Mailing list"
-          @url={{@crate.mailing_list}}
-        />
-      {{/if}}
-
       {{#if @version.documentationLink}}
         <CrateSidebar::Link
           @title="Documentation"

app/models/crate.js

@@ -14,9 +14,6 @@ export default class Crate extends Model {
 
   @attr description;
   @attr homepage;
-  @attr wiki;
-  @attr mailing_list;
-  @attr issues;
   @attr documentation;
   @attr repository;
   @attr exact_match;