You can try removing it in each track using Paul Hoad's Track Editor.
Find the pit section that has the "Pitlane Speed Limiter On" command, left-click on it to select it, right-click on it to open the pop-up menu and choose "Cut". Cut also the "Pitlane Speed Limiter Off" command to be sure. Then save the track. Be aware that if the track has any magic data, this will remove it so you will have to re-insert it. I have never tried removing these commands so I can't predict the results. Just be logical and back-up your track file first.