MudBaseDatePicker: Don't try to highlight invalid dates

[Anu6is]

Description

Highlighted date fails if an invalid fixed day is provided for the current month.

The unit test regarding this scenario was updated to consistently test an invalid fixed date for a predefined current day.
The test passed previously as it simply tested fixed date only, meaning it succeeded in months with 31 days.

How Has This Been Tested?

Unit tests

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.85%. Comparing base (13a89f8) to head (524da4e).
Report is 2 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #10785      +/-   ##
==========================================
+ Coverage   91.83%   91.85%   +0.01%     
==========================================
  Files         427      427              
  Lines       13430    13431       +1     
  Branches     2592     2593       +1     
==========================================
+ Hits        12334    12337       +3     
  Misses        523      523              
+ Partials      573      571       -2     

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[mikes-gh]

if (DateTime.TryParseExact($"{year}-{month}-{day}", "yyyy-M-d", Culture, DateTimeStyles.None, out var date))
{
    HighlightedDate = date
}

Might read a bit easier?

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[mikes-gh]

Thanks . Nice use of FakeTimeProvider