fix(scripts/Felmyst): Adjust beam target

[Si1ker]

Change the way Felmyst selects the target for the beam which summons skeletons at the encounter.

All available players get one beam ❌
Only one player gets one beam ✔️

Sources:

• https://www.youtube.com/watch?v=zKIepv2-Yjo (since 1:45: Only one target runs from the beam)
• https://wowwiki.fandom.com/wiki/Felmyst "She will target a random player for a couple of seconds"

Changes Proposed:

• Convert CastSpell to CastCustomSpell in order to prevent AOE targets and just pick one valid target

Issues Addressed:

• Felmyst currently summons one beam per player available in the encounter instead of pick just one as the expected blizzlike behavior

Tests Performed:

• Tested in-game locally and with a production/live server in the past.
  

How to Test the Changes:

You will need to bring 2 accounts and make a raid group
.go c felmyst
Kill Brutallus
Wait for >1 minute until Felmyst spawns
Engage Felmyst and wait for her Phase 2 -> She will target only 1 of your 2 characters as the blizzlike behavior.

Known Issues and TODO List:

• N/A

Target Branch(es):

• Master

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[BarbzYHOOL]

nice