Stop using ResourceContext::GetHostResolver()

https://chromium-review.googlesource.com/c/chromium/src/+/1135366

atom/browser/net/url_request_context_getter.cc

@@ -207,12 +207,6 @@ class ResourceContext : public content::ResourceContext {
   ResourceContext() = default;
   ~ResourceContext() override = default;
 
-  net::HostResolver* GetHostResolver() override {
-    if (request_context_)
-      return request_context_->host_resolver();
-    return nullptr;
-  }
-
   net::URLRequestContext* GetRequestContext() override {
     return request_context_;
   }