Revert "Use rmdirSync instead of rimraf"

This reverts commit a7ae58f4db.

This change requires node12, but we still support building on older node
versions

extensions/postinstall.js

@@ -8,6 +8,7 @@
 
 const fs = require('fs');
 const path = require('path');
+const rimraf = require('rimraf');
 
 const root = path.join(__dirname, 'node_modules', 'typescript');
 
@@ -20,7 +21,7 @@ function processRoot() {
 		if (!toKeep.has(name)) {
 			const filePath = path.join(root, name);
 			console.log(`Removed ${filePath}`);
-			fs.rmdirSync(filePath, { recursive: true });
+			rimraf.sync(filePath);
 		}
 	}
 }