This fixes#1438.
Note however, that using a pager such as less will add a newline itself.
So to actually not print a newline for such files, you need to either
disable paging:
bat --style=plain --paging=never no-newline-at-end-of-file.txt
or use a "pager" that does not add a newline:
bat --style=plain --pager=cat no-newline-at-end-of-file.txt
Note that we also update syntax tests file since a bunch of them had
missing newlines on the last lines.
