[Windows]Remove fill property in back-to-top icon

[yanwa4]

Description

Remove fill property of back-to-top icon

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots:

Before (If applicable):

After:

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 change)
• [ ] Documentation update
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (b4234b4) 94.12% compared to head (2836aec) 94.18%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1513 +/- ## ========================================== + Coverage 94.12% 94.18% +0.05% ========================================== Files 134 134 Lines 18988 18988 Branches 2905 2899 -6 ========================================== + Hits 17873 17884 +11 + Misses 1115 1104 -11 ```

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