lintian.d.o: fix deflate output filter

lintian.d.o: fix deflate output filter

It appears that AddOutputFilterByType options also apply to the
subdirectories. However this directive overwrites the default value or
the one defined in the parent directory.

Therefore we only want to add this directive to the root directory and
with all the mime types.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>