fix(Attachment): do not render progress value

[levithomason]

Fixes #385

This PR prevents the Attachment's progress value from the rendered to the DOM. It is only used for styling purposes.

Before

After

[codecov]

Codecov Report

Merging #402 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #402   +/-   ##
=======================================
  Coverage   91.72%   91.72%           
=======================================
  Files          41       41           
  Lines        1341     1341           
  Branches      197      197           
=======================================
  Hits         1230     1230           
  Misses        107      107           
  Partials        4        4

Impacted Files	Coverage Δ
src/components/Attachment/Attachment.tsx	97.14% <0%> (ø)	⬆️

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