bug: keyboard pages redirect current-version to a .php extension, but the .php extension should never be shown in the address bar

[mcdurdin]

e.g. https://help.keyman.com/keyboard/khmer_angkor/current-version
redirects to https://help.keyman.com/keyboard/khmer_angkor/1.5/khmer_angkor.php

It should redirect to: https://help.keyman.com/keyboard/khmer_angkor/1.5/khmer_angkor

https://help.keyman.com/keyboard/khmer_angkor/1.5/khmer_angkor.php should also redirect to https://help.keyman.com/keyboard/khmer_angkor/1.5/khmer_angkor