Fix migration causing stat AEs to be miscalculated

Intent

We were accidentally duplicating the modified stat values and then updating the actor with said stat values. This changed the base stat value, which the AEs recalculate on top of, causing the issue.

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• This is meant for a hotfix
• This is meant for the next release (see milestone)
• This needs more reviewers than normal; there may be controversy or high complexity
• This intentionally introduces regressions that will be addressed later
• There is/will be documentation changes on the wiki
• Please do not send commits here without coordinating closely with the owner
• This is a Build System change

Related Issues

• #908 (closed)

Steps to Test

1. In v10/v0.87.6 Create a Character
   • BODY: 6
2. Add/Install Grafted Muscle and Bone Lace
   • BODY: 8
3. Load v11/v0.88.1
4. Let migrations finish
5. Check Character
   • BODY: 8