Remove last exec_ instances, add archive deletion test, retain archive deletion message

[samuel-w]

That should be the last of the dialog exec_.

I'm doing this to prepare for PyQt6 https://riverbankcomputing.com/software/pyqt/download.

[codecov-io]

Codecov Report

Merging #722 (931a1e9) into master (39b7f58) will increase coverage by 1.24%.
The diff coverage is 86.36%.

@@            Coverage Diff             @@
##           master     #722      +/-   ##
==========================================
+ Coverage   73.50%   74.74%   +1.24%     
==========================================
  Files          52       52              
  Lines        3378     3374       -4     
==========================================
+ Hits         2483     2522      +39     
+ Misses        895      852      -43     

Impacted Files	Coverage Δ
src/vorta/__main__.py	0.00% <0.00%> (ø)
src/vorta/application.py	68.93% <0.00%> (ø)
src/vorta/views/repo_tab.py	81.17% <71.42%> (+8.23%)	⬆️
src/vorta/views/archive_tab.py	84.71% <100.00%> (+3.35%)	⬆️
src/vorta/views/extract_dialog.py	96.49% <100.00%> (+9.72%)	⬆️
src/vorta/views/main_window.py	84.24% <100.00%> (+0.10%)	⬆️
src/vorta/views/repo_add_dialog.py	69.02% <100.00%> (+0.27%)	⬆️
src/vorta/utils.py	61.74% <0.00%> (-2.74%)	⬇️
... and 2 more

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[m3nu]

Thanks! Looks like a good cleanup.