feat: delete custom user attributes from events

[zhu-xiaowei]

Description

1. delete custom user attributes from events

General Checklist

• Added new tests to cover change, if needed
• Build succeeds using Swift Package Manager
• All unit tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (87a0e7f) 94.78% compared to head (2f44e47) 94.67%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
- Coverage   94.78%   94.67%   -0.11%     
==========================================
  Files          35       35              
  Lines        1916     1935      +19     
==========================================
+ Hits         1816     1832      +16     
- Misses        100      103       +3     

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