repl: use more readable RegExp syntax for spaces

This is just a cosmetic change really, nothing major.

lib/repl.js

@@ -924,5 +924,5 @@ function isSyntaxError(e) {
       !e.match(/^SyntaxError: .*strict mode.*/i) &&
       // JSON.parse() error
       !(e.match(/^SyntaxError: Unexpected (token .*|end of input)/) &&
-      e.match(/\n    at Object.parse \(native\)\n/));
+      e.match(/\n {4}at Object.parse \(native\)\n/));
 }