docs: simplify a link in the html front page
docs: simplify a link in the html front page

index.html and gcode.html live in the same directory: the root of the
generated html tree.  So there's no need to bounce around directories
when linking.

mhaberler/machinekit,ianmcmahon/linuxcnc-mirror,cdsteinkuehler/linuxcnc,unseenlaser/linuxcnc,unseenlaser/machinekit,aschiffler/linuxcnc,ArcEye/MK-Qt5,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,cdsteinkuehler/linuxcnc,araisrobo/machinekit,araisrobo/machinekit,kinsamanka/machinekit,ianmcmahon/linuxcnc-mirror,cdsteinkuehler/MachineKit,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,kinsamanka/machinekit,cdsteinkuehler/linuxcnc,bmwiedemann/linuxcnc-mirror,jaguarcat79/ILC-with-LinuxCNC,cdsteinkuehler/MachineKit,Cid427/machinekit,unseenlaser/machinekit,cdsteinkuehler/MachineKit,araisrobo/machinekit,araisrobo/machinekit,kinsamanka/machinekit,Cid427/machinekit,RunningLight/machinekit,EqAfrica/machinekit,unseenlaser/linuxcnc,ikcalB/linuxcnc-mirror,Cid427/machinekit,ianmcmahon/linuxcnc-mirror,ArcEye/machinekit-testing,RunningLight/machinekit,RunningLight/machinekit,Cid427/machinekit,strahlex/machinekit,bmwiedemann/linuxcnc-mirror,EqAfrica/machinekit,ikcalB/linuxcnc-mirror,ArcEye/MK-Qt5,araisrobo/machinekit,ArcEye/MK-Qt5,ArcEye/machinekit-testing,kinsamanka/machinekit,strahlex/machinekit,ianmcmahon/linuxcnc-mirror,unseenlaser/linuxcnc,bmwiedemann/linuxcnc-mirror,ArcEye/machinekit-testing,kinsamanka/machinekit,EqAfrica/machinekit,mhaberler/machinekit,cdsteinkuehler/MachineKit,cdsteinkuehler/MachineKit,RunningLight/machinekit,strahlex/machinekit,EqAfrica/machinekit,aschiffler/linuxcnc,jaguarcat79/ILC-with-LinuxCNC,unseenlaser/machinekit,RunningLight/machinekit,mhaberler/machinekit,Cid427/machinekit,unseenlaser/machinekit,EqAfrica/machinekit,mhaberler/machinekit,Cid427/machinekit,aschiffler/linuxcnc,cdsteinkuehler/linuxcnc,aschiffler/linuxcnc,araisrobo/machinekit,bmwiedemann/linuxcnc-mirror,araisrobo/machinekit,EqAfrica/machinekit,unseenlaser/machinekit,mhaberler/machinekit,ArcEye/MK-Qt5,ikcalB/linuxcnc-mirror,Cid427/machinekit,ArcEye/machinekit-testing,cdsteinkuehler/MachineKit,aschiffler/linuxcnc,RunningLight/machinekit,EqAfrica/machinekit,ArcEye/machinekit-testing,bobvanderlinden/machinekit,mhaberler/machinekit,strahlex/machinekit,ArcEye/MK-Qt5,ianmcmahon/linuxcnc-mirror,ianmcmahon/linuxcnc-mirror,ArcEye/machinekit-testing,bobvanderlinden/machinekit,mhaberler/machinekit,bobvanderlinden/machinekit,EqAfrica/machinekit,unseenlaser/linuxcnc,bmwiedemann/linuxcnc-mirror,RunningLight/machinekit,ianmcmahon/linuxcnc-mirror,kinsamanka/machinekit,strahlex/machinekit,bobvanderlinden/machinekit,strahlex/machinekit,unseenlaser/machinekit,unseenlaser/machinekit,ArcEye/MK-Qt5,RunningLight/machinekit,ikcalB/linuxcnc-mirror,narogon/linuxcnc,unseenlaser/linuxcnc,narogon/linuxcnc,ArcEye/MK-Qt5,Cid427/machinekit,unseenlaser/machinekit,jaguarcat79/ILC-with-LinuxCNC,bobvanderlinden/machinekit,jaguarcat79/ILC-with-LinuxCNC,araisrobo/machinekit,jaguarcat79/ILC-with-LinuxCNC,cdsteinkuehler/linuxcnc,bmwiedemann/linuxcnc-mirror,narogon/linuxcnc,kinsamanka/machinekit,narogon/linuxcnc,strahlex/machinekit,bobvanderlinden/machinekit,ArcEye/MK-Qt5,ikcalB/linuxcnc-mirror,kinsamanka/machinekit,bobvanderlinden/machinekit,bmwiedemann/linuxcnc-mirror,narogon/linuxcnc,araisrobo/machinekit,mhaberler/machinekit,ArcEye/machinekit-testing,ArcEye/machinekit-testing