This is already inside SYSADMIN_PARTS, so there is no need
to add that twice.
pve-usbstick-plain.html \
getting-help-plain.html \
pve-system-requirements-plain.html \
pve-usbstick-plain.html \
getting-help-plain.html \
pve-system-requirements-plain.html \
- system-timesync-plain.html \
$(addsuffix -plain.html, ${SYSADMIN_PARTS}) \
$(addsuffix -plain.html, ${CHAPTER_LIST}) \
$(addsuffix .5-plain.html, ${CONFIG_LIST}) \
$(addsuffix -plain.html, ${SYSADMIN_PARTS}) \
$(addsuffix -plain.html, ${CHAPTER_LIST}) \
$(addsuffix .5-plain.html, ${CONFIG_LIST}) \