[lua] Fix Blue Magic from skipping MDT

[Skold177]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

• Adds a missing xi.combat.damage.calculateDamageAdjustment to applySpellDamage in bluemagic,lua. Above comment makes reference to "Handling MDT" but never runs it through the function needed to do it.

Steps to test these changes

Use 1000 Needles, see MDT works against it now.

[Xaver-DaRed]

Blue magic needs the same treatment regular magic got.

This function (not the MDT function, the function youve placed in) would equate to the "final magic adjustment" step in the old magic system.

This would not be the step to place it.

I also have doubts about physical, breath and ranged blue spells use MDT indiscriminatedly. And even if it did, we would still need to check if the other "damage taken" forms affect it.

[Butsuon]

At least for Breath BLU magic, this is testable against Jourm and Khim, who have +50 and -50 respectively according to Jimmay's sheet.

Find dude --> breathe on dude --> observe