Revert "Collect and upload coverage on appveyor"
Revert "Collect and upload coverage on appveyor"

This reverts commit 8c996585125564d1458ed87d463974d4ac0ae2bf.

luacov-coveralls + appveyor are seemingly as broken as they used to be.

mpeterv/luacheck,mpeterv/luacheck,mpeterv/luacheck,xpol/luacheck,xpol/luacheck,xpol/luacheck