Documentation: remove networking/.gitignore

Remove empty networking/.gitignore
Signed-off-by: NPeter Foley <pefoley2@pefoley.com>
Cc: rdunlap@infradead.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>