Replace rimraf with fs.rmSync in postinstall

The postinstall gets ran when you install with npm but rimraf is a development
dependency so it will not exist.

Index: code-server/lib/vscode/extensions/postinstall.js
===================================================================
--- code-server.orig/lib/vscode/extensions/postinstall.js
+++ code-server/lib/vscode/extensions/postinstall.js
@@ -8,7 +8,6 @@
 
 const fs = require('fs');
 const path = require('path');
-const rimraf = require('rimraf');
 
 const root = path.join(__dirname, 'node_modules', 'typescript');
 
@@ -21,7 +20,7 @@ function processRoot() {
 		if (!toKeep.has(name)) {
 			const filePath = path.join(root, name);
 			console.log(`Removed ${filePath}`);
-			rimraf.sync(filePath);
+			fs.rmSync(filePath, { recursive: true });
 		}
 	}
 }