removed cpx from theia-core's dev deps
removed cpx from theia-core's dev deps

Signed-off-by: Anton Kosiakov <93305abb4fd19156b2366e8285c439930563a735@typefox.io>

epatpol/theia-1,lmcgupe/theiagreenkeeperTest,hexa00/theia,lmcgupe/theiagreenkeeperTest,lmcgupe/theiagreenkeeperTest,lmcgupe/theia,hexa00/theia,epatpol/theia-1,epatpol/theia-1,lmcgupe/theia