Use CCsettings to remove all badge count (can remove if you don't use it), then with iCleaner Pro disable the OTA Software Update. This method clears and permanently stops it from coming back.
or
(risky)
Navigate to /Applications/Preferences.app and open General.plist
Remove: the <dict> to </dict> where SOFTWARE_UPDATE is contained to completely remove that the Software Update tab from Settings update. To just remove it from badging, remove the <key>cellClass to the PSBadgedTableCell</key>
You can add a letter in the end or rename it instead of deleting it. But you still need to clear the badge count with CCsettings first.