MudTextField: Remove last remaining reference to KeyPress

[danielchalmers]

Description

Follow up to #8476

How Has This Been Tested?

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.
• I've added relevant tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.30%. Comparing base (6c6f610) to head (4c5b52b).
Report is 3 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #8516   +/-   ##
=======================================
  Coverage   89.29%   89.30%           
=======================================
  Files         411      411           
  Lines       11901    11901           
  Branches     2356     2356           
=======================================
+ Hits        10627    10628    +1     
  Misses        751      751           
+ Partials      523      522    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[henon]

Thanks Daniel