fix(DB/Loot) Clean up loot of bosses in MGT HC

[Tereneckla]

Changes Proposed:

This PR proposes changes to:

• Core (units, players, creatures, game systems).
• Scripts (bosses, spell scripts, creature scripts).
• Database (SAI, creatures, etc).

Remove Normal loot from all HC Bosses
Group items of Kael'thas

Issues Addressed:

• Closes [Magister's Terrace] All bosses in heroic drops their normal loot #21259

SOURCE:

The changes have been validated through:

• Live research (checked on live servers, e.g Classic WotLK, Retail, etc.)
• Sniffs (remember to share them with the open source community!)
• Video evidence, knowledge databases or other public sources (e.g forums, Wowhead, etc.)
• The changes promoted by this pull request come partially or entirely from another project (cherry-pick). Cherry-picks must be committed using the proper --author tag in order to be accepted, thus crediting the original authors, unless otherwise unable to be found

Counting drops in multiple videos

https://youtu.be/vRjgCtDOzo8
https://youtu.be/eps9m8S4cLc
https://youtu.be/nKSSYAkpW_s
https://youtu.be/o1FaN1_JIug
https://youtu.be/4ZHh5UhkGIE
https://youtu.be/My5ZrCZ8mok
https://youtu.be/L-eWJ_TdMSE
https://youtu.be/g5oA9_0s8CY
https://youtu.be/kVF_Di5CRKo
https://youtu.be/xkJysd5YOHI
https://youtu.be/C7nMa-cM4pI
https://youtu.be/13EsTeJmiPQ
https://youtu.be/kfZoZ5EVNCo
https://youtu.be/AN27RLSZXu4
https://youtu.be/eFILcvIVrEo
https://youtu.be/9MierCOmCmA
https://youtu.be/sQFQbzAk-7s
https://youtu.be/GJcy8cK0d10
https://youtu.be/CTddhJ9g5Lk

Tests Performed:

This PR has been:

• Tested in-game by the author.
• Tested in-game by other community members/someone else other than the author/has been live on production servers.
• This pull request requires further testing and may have edge cases to be tested.

How to Test the Changes:

• This pull request can be tested by following the reproduction steps provided in the linked issue
• This pull request requires further testing. Provide steps to test your changes. If it requires any specific setup e.g multiple players please specify it as well.

Known Issues and TODO List:

• [ ]
• [ ]

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