Bug#1072349: lua-resty-lrucache: replace luajit2 with luajit

[Chris Hofstaedtler]

Source: lua-resty-lrucache
Version: 0.13-10
Severity: serious
Control: block 1069780 by -1

luajit2 was requested to be removed, see #1069780. Please switch
your (Build-Depends) over to luajit, which has become the openresty
luajit(2) source.