fix typo in filetype.py
fix typo in filetype.py

SRI-CSL/whole-program-llvm,travitch/whole-program-llvm,SRI-CSL/whole-program-llvm,SRI-CSL/whole-program-llvm,travitch/whole-program-llvm,travitch/whole-program-llvm,SRI-CSL/whole-program-llvm,travitch/whole-program-llvm,SRI-CSL/whole-program-llvm