Make skill rust related mutations display as mixed effect

[RenechCDDA]

Summary

None

Purpose of change

These traits have not been updated since skill rust became a net bonus for characters. Having good memory is displayed as a wholly positive mutation, despite the fact it will slow down your skill growth. It even costs 3 points(!) despite the detrimental effect on your character.

Describe the solution

Change them both to mixed_effect so they display as purple

Change point costs to 0

Also updated the description for forgetfulness to mention its effect on your ability to lie.

Describe alternatives you've considered

Swapping the colors completely so that good memory is properly shown as a negative

Testing

Additional context