Fix spawning code-server within code-server (#4590)

* Remove extra VS Code CLI spawn

We already spawn VS Code's CLI when necessary in the lines below.
Having the CLI spawn unconditionally when in a VS Code environment makes
it impossible to run code-server within code-server (for example to
develop it).

* Update VS Code

This sanitizes our environment variables so code-server does not always
think it is a child spawn.

Fixes https://github.com/cdr/code-server/issues/4519.

vendor/package.json

@@ -7,6 +7,6 @@
     "postinstall": "./postinstall.sh"
   },
   "devDependencies": {
-    "code-oss-dev": "cdr/vscode#5e0c6f3b95ed032e62c49101ae502a46c62ef202"
+    "code-oss-dev": "cdr/vscode#c2a251c6afaa13fbebf97fcd8a68192f8cf46031"
   }
 }