FileUpload: Fix top margin CSS

[danielchalmers]

Description

This is a resubmit of #6483 with formatting updates from the dev branch included

Tracked under #8435

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 88.75%. Comparing base (9937991) to head (a47874c).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8438      +/-   ##
==========================================
+ Coverage   88.73%   88.75%   +0.02%     
==========================================
  Files         416      416              
  Lines       12372    12372              
  Branches     2459     2459              
==========================================
+ Hits        10978    10981       +3     
+ Misses        862      860       -2     
+ Partials      532      531       -1     

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