contrib/gitdm: filetype interface is not in order, fix

contrib/gitdm: filetype interface is not in order, fix

gitm prints the rather cryptic message "interface not found, appended
to the last order".  This is because filetypes.txt has filetype
interface, but neglects to mention it in order.  Fix that.

Fixes: 2f28271d807edfcdc47a280c06999dd866dcae10
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Message-Id: <20190822122350.29852-2-armbru@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>