JsEvent: Use IAsyncDisposable

[ScarletKuro]

Description

Logic aligns with the rest of the services

Type of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (fix or improvement to the website or code docs)

Checklist

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[ScarletKuro]

Added to the v8 migration guide at #9953

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.17%. Comparing base (65c064b) to head (2b6ca16).
Report is 1 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #10061      +/-   ##
==========================================
- Coverage   91.17%   91.17%   -0.01%     
==========================================
  Files         410      410              
  Lines       12471    12463       -8     
  Branches     2420     2419       -1     
==========================================
- Hits        11371    11363       -8     
  Misses        555      555              
  Partials      545      545              

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