Remove Node browser shim

We used this to run vscodevim in the browser but it now has a version
that is able to run as a VS Code web extension. This does require an
update to our marketplace, however.

lib/vscode/src/vs/workbench/api/browser/extensionHost.contribution.ts

@@ -61,7 +61,6 @@ import './mainThreadComments';
 import './mainThreadNotebook';
 import './mainThreadTask';
 import './mainThreadLabelService';
-import 'vs/server/browser/mainThreadNodeProxy';
 import './mainThreadTunnelService';
 import './mainThreadAuthentication';
 import './mainThreadTimeline';