Alert: Remove AlertTextPosition

[ScarletKuro]

Description

After this PR #8532 it's not used anymore

Types 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)

Checklist

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.

[danielchalmers]

Ha got there just before me 😀

I was going to check the whole codebase for unused code. Do you know if there's any more?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.88%. Comparing base (28bc599) to head (f4fab9c).
Report is 19 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8637      +/-   ##
==========================================
+ Coverage   89.82%   89.88%   +0.05%     
==========================================
  Files         412      414       +2     
  Lines       11878    11913      +35     
  Branches     2364     2364              
==========================================
+ Hits        10670    10708      +38     
+ Misses        681      675       -6     
- Partials      527      530       +3     

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[ScarletKuro]

Added to v7.0.0 Migration Guide #8447 under "Others"