Fixed Trade Stats phpBB debug warning

Device: PC
Browser: Chrome 94.0.4606.81 and Edge 95.0.1020.30
OS: Windows 10

Steps to reproduce: Go to trade-stats.php by entering the URL or clicking the "Trade Stats" button.

Anything else to add:
[phpBB Debug] PHP Warning: in file [ROOT]/tradestats_last5.php on line 33: date() expects parameter 2 to be int, string given

at the top of the Last 10 trades completed list see screenshot.

Aware of this bug - already 5 or so reports on it. Read please before posting the same issue again.