Fix for #2577 - Swap pads 3 and 4 of R_Shunt_Ohmite_LVK*

This change swaps pads 3 and 4 of R_Shunt_Ohmite_LVK series of fps. These fps have two pads on the same physical contact, to enable current measurement on a shunt. Because the pads that match the shunt symbol are diagonally across, they are very inconvenient to route with that symbol. Swapping the pads has no effect on the fp as they are identical, but makes it compatible with the standard shunt symbol in the library. More details in #2577 (closed).

The change also removes an inexplicably set die length from one of the pads in LVK12.

Fixes #2577 (closed).