Fix The Dark Seer's "Unaffected by Blind"

[Helyos96]

Also rename the old flag "IgnoreBlindHitChance" to "UnaffectedByBlind" for clarity (no functional change)

Description of the problem being solved:

The Dark Seer's blind modifier is "Unaffected by Blind". It was renamed from older versions which used to say "blind does not affect your chance to hit".

The unique rework ff5eb7e: "Port unique updater scripts from PoB2 (#9480)" changed it to "Cannot be Blinded" which is not quite the same.

Steps taken to verify a working solution:

• Equipped The Dark Seer and verified that the build is correctly considered unaffected by blind, but still blind.

[Helyos96]

Just in case, the Spell Checker triggered on an existing word that's pretty far away from my changes, so I'm leaving it as-is.