Remove obsolete -f flag for neovim

Author: vimpostor

tests/Makefile

@@ -3,4 +3,4 @@ tests: tests_vim tests_neovim
 tests_vim:
 	PATH=./:${PATH} vim -f --not-a-term -u vimrc -S run_test.vim test_general.vim || ( cat *.failed.log && false )
 tests_neovim:
-	PATH=./:${PATH} nvim -f -u vimrc -S run_test.vim test_general.vim || ( cat *.failed.log && false )
+	PATH=./:${PATH} nvim -u vimrc -S run_test.vim test_general.vim || ( cat *.failed.log && false )