Hello,
Thank you for your feedback.
Indeed there is a missing feature to remove the update site from the Joomla database.
You can do it manually by accessing your database for the table "..._update_sites".
Best is to locate the entry for HikaMarket and change the value for the "enabled" column from "1" to "0".
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.