'Mech Medium Shields incorrectly prevent Jump Jets as of 0.7.6

[Naibuno]

SSW 0.7.6 gives the jumping penalties of heavy shields to medium shields

Per TacOps (last updated 6 December 2019), heavy shields greatly reduce movement and prevent jumping, while medium shields only slightly reduce movement without preventing jumping, and light shields impede neither.

Another bug with shields: Issue 322 mentions shields' penalties applying to all OmniMechs when one variant has one equipped.