fix(Scripts/Arenas): Updating timer for Shadow Sight spawns

[Knindzagxg]

Changes Proposed:

This PR proposes changes to:

• [x] Core (units, players, creatures, game systems).

Issues Addressed:

• Closes #17119

SOURCE:

The changes have been validated through:

• [x] Live research (checked on live servers, e.g Classic WotLK, Retail, etc.)
• [x] Video evidence, knowledge databases or other public sources (e.g forums, Wowhead, etc.)

Tests Performed:

This PR has been:

• [x] Tested in-game by the author.

How to Test the Changes:

• [x] This pull request can be tested by following the reproduction steps provided in the linked issue

1. Log ingame with 2 accounts
2. .debug arena and then join skirmish
3. Use /timer to see when will Shadow Sight(s) spawn

Known Issues and TODO List:

• [ ]
• [ ]

How to Test AzerothCore PRs

When a PR is ready to be tested, it will be marked as [WAITING TO BE TESTED].

You can help by testing PRs and writing your feedback here on the PR's page on GitHub. Follow the instructions here:

http://www.azerothcore.org/wiki/How-to-test-a-PR

REMEMBER: when testing a PR that changes something generic (i.e. a part of code that handles more than one specific thing), the tester should not only check that the PR does its job (e.g. fixing spell XXX) but especially check that the PR does not cause any regression (i.e. introducing new bugs).

For example: if a PR fixes spell X by changing a part of code that handles spells X, Y, and Z, we should not only test X, but we should test Y and Z as well.

[pvp100com]

The update has been applied to my server, and it has been running stable for a week.