MNT: Delete PNG icon

[pllim]

PNG icon is no longer needed. This is a direct follow-up of #678

[codecov]

Codecov Report

Merging #679 (a064b7d) into main (664d35b) will decrease coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #679      +/-   ##
==========================================
- Coverage   59.75%   59.60%   -0.15%     
==========================================
  Files          65       65              
  Lines        4005     4005              
==========================================
- Hits         2393     2387       -6     
- Misses       1612     1618       +6     

Impacted Files	Coverage Δ
...configs/default/plugins/data_tools/file_chooser.py	65.71% <0.00%> (-3.43%)	⬇️

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