fix(dashboard): Hide download backup dialog box after success (backport #4883)

[mergify]

fixes: #4396

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This is an automatic backport of pull request #4883 done by Mergify.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.95%. Comparing base (320c643) to head (bdb7af6).

Files with missing lines	Patch %	Lines
dashboard/src/objects/site.js	0.00%	2 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4895      +/-   ##
==========================================
- Coverage   72.95%   72.95%   -0.01%     
==========================================
  Files         101      101              
  Lines       15986    15987       +1     
  Branches      284      284              
==========================================
  Hits        11663    11663              
- Misses       4295     4296       +1     
  Partials       28       28              

Flag	Coverage Δ
dashboard	72.95% <0.00%> (-0.01%)	⬇️

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