Restyle remote: base: download: don't walk dir twice

[restyled-io]

Automated style fixes for #2909, created by Restyled.

The following restylers made fixes:

• black

To incorporate these changes, merge this Pull Request into the original. We
recommend using the Squash or Rebase strategies.

NOTE: As work continues on the original Pull Request, this process will
re-run and update (force-push) this Pull Request with updated style fixes as
necessary. If the style is fixed manually at any point (i.e. this process finds
no fixes to make), this Pull Request will be closed automatically.

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (efiop-patch-1@5251171). Click here to learn what that means.
The diff coverage is 100%.

@@               Coverage Diff                @@
##             efiop-patch-1    #2910   +/-   ##
================================================
  Coverage                 ?   91.28%           
================================================
  Files                    ?      137           
  Lines                    ?     8550           
  Branches                 ?        0           
================================================
  Hits                     ?     7805           
  Misses                   ?      745           
  Partials                 ?        0

Impacted Files	Coverage Δ
dvc/remote/base.py	94.59% <100%> (ø)

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