Update pl_PL.lang

I removed two lines because those were doubles of already existing lines:
item.fuelCanister.name=Kanister Pe\u0142en Paliwa
item.oilExtractor.name=Przeno\u015Bny Ekstraktor Ropy
item.fuelCanister.name=Filled Fuel Canister
item.oilExtractor.name=Portable Oil Extractor

My translation is not finished yet. I'm planning on translating this whole stuff. Also it's my first time translating stuff so advice would be nice (for example what to do with polish letters).
Also a lot of stuff is repeating. Not sure if that is necessary.