Remove stray __init__.py file from plugins dir
Remove stray __init__.py file from plugins dir

Since it completely breaks plugin loading as the plugin system thinks it
is a plugin it needs to load.

Fixes CURA-3041

fieldOfView/Cura,ynotstartups/Wanhao,Curahelper/Cura,ynotstartups/Wanhao,fieldOfView/Cura,hmflash/Cura,hmflash/Cura,Curahelper/Cura