fix(lib/vscode): remove native-keymap and keytar (#2961)

native-keymap and keytar are only used in the electron process,
so we don't need them. This allows us to drop our dependencies on
libx11-dev, libxkbfile-dev, and libsecret-dev.

lib/vscode/extensions/github-authentication/src/typings/ref.d.ts

@@ -5,3 +5,6 @@
 
 /// <reference path='../../../../src/vs/vscode.d.ts'/>
 /// <reference path='../../../../src/vs/vscode.proposed.d.ts'/>
+/// <reference path='../../../../src/typings/keytar.d.ts'/>
+
+// NOTE@coder: add keytar typeref