test: update emacs test to use test_expect_equal_file

test: update emacs test to use test_expect_equal_file

This is a much cleaner way to do the emacs tests, since we're actually
comparing output against existing files with expected output.  We also
won't miss any trailing newlines this way.

And speaking of which, one of the expected output files was actually
missing a trailing blank line that was actually in one of the original
messages, so this was fixed.