Replace fs-extra with fs.promises

Remove the Mac directory copy instead of refactoring it since we've had
this for a long time now and I think it's safe to assume that users
running code-server on Mac don't have the old directory anymore.

package.json

@@ -38,7 +38,6 @@
     "@types/compression": "^1.7.0",
     "@types/cookie-parser": "^1.4.2",
     "@types/express": "^4.17.8",
-    "@types/fs-extra": "^8.0.1",
     "@types/http-proxy": "^1.17.4",
     "@types/js-yaml": "^3.12.3",
     "@types/node": "^12.12.7",
@@ -83,7 +82,6 @@
     "cookie-parser": "^1.4.5",
     "env-paths": "^2.2.0",
     "express": "^5.0.0-alpha.8",
-    "fs-extra": "^9.0.1",
     "http-proxy": "^1.18.0",
     "httpolyglot": "^0.1.2",
     "js-yaml": "^3.13.1",