Fix wrong default path in repl.js

shouma already had some problems after pulling a server update:

```
CRASH: Error: ENOENT, no such file or directory './repl'
    at Object.fs.readdirSync (fs.js:665:18)
    at Object.exports.start (/home/shouma/showdown/Pokemon-Showdown/repl.js:20:6)
    at Object.<anonymous> (/home/shouma/showdown/Pokemon-Showdown/team-validator.js:156:23)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3
```