fix: remove temp dir if installer fails to download

[jahzielv]

For #25373

Checklist for submitter

If some of the following don't apply, delete the relevant line.

• Changes file added for user-visible changes in changes/, orbit/changes/ or ee/fleetd-chrome/changes.
  See Changes files for more information.
• Added/updated automated tests
• A detailed QA plan exists on the associated ticket (if it isn't there, work with the product group's QA engineer to add it)
• Manual QA for all new/changed functionality
• For Orbit and Fleet Desktop changes:
  • Orbit runs on macOS, Linux and Windows. Check if the orbit feature/bugfix should only apply to one platform (runtime.GOOS).
  • Manual QA must be performed in the three main OSs, macOS, Windows and Linux.
  • Auto-update manual QA, from released version of component to new version (see tools/tuf/test).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.58%. Comparing base (e80034e) to head (a52c93d).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25392      +/-   ##
==========================================
+ Coverage   63.55%   63.58%   +0.02%     
==========================================
  Files        1618     1619       +1     
  Lines      154473   154836     +363     
  Branches     4037     4037              
==========================================
+ Hits        98174    98448     +274     
- Misses      48562    48628      +66     
- Partials     7737     7760      +23     

Flag	Coverage Δ
backend	64.42% <100.00%> (+0.02%)	⬆️

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[iansltx]

Looks reasonable. Approved once a changes file is added, and can be merged once we're out of the fleetd freeze.

[iansltx]

Will need to be merged after the fleetd freeze is lifted, but it's ready!