Tweaks to modern theme single file attachment

[Blackbaud-TrevorBurch]

No description provided.

[blackbaud-ado]

Preview build at https://developer.blackbaud.com/skyux-forms?_sp.spa=pr-single-file-attachment-modern-tweaks

[codecov]

Codecov Report

Merging #237 (f3d5ef2) into master (fe6377c) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #237   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           29        29           
  Lines          884       881    -3     
  Branches       169       168    -1     
=========================================
- Hits           884       881    -3     

Impacted Files	Coverage Δ
...file-attachment/file-attachment-label.component.ts	100.00% <100.00%> (ø)

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