refactor: drop duplicate NewNormalVector method

[Goodnight77]

description:

• remove duplicate NewNormalVector method. it had the same body as NormalVector
• NormalMatrix updated to call NormalVector.

[Copilot]

Pull request overview

This PR removes a duplicate random-vector generator method on util.RandomGenerator and updates NormalMatrix to use the remaining implementation, reducing redundant code in the common/util helpers used across model/dataset components.

Changes:

• Remove the duplicate NewNormalVector method implementation.
• Keep a single NormalVector implementation for generating normally-distributed []float32.
• Update NormalMatrix to call NormalVector.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.96%. Comparing base (1dac895) to head (671fdad).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1257   +/-   ##
=======================================
  Coverage   72.95%   72.96%           
=======================================
  Files          91       91           
  Lines       16720    16715    -5     
=======================================
- Hits        12198    12196    -2     
+ Misses       3278     3275    -3     
  Partials     1244     1244           

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