Update images in multi-graph matching examples

[codecov[bot]]

Codecov Report

Merging #82 (2ff55a1) into main (762eee8) will increase coverage by 0.02%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #82      +/-   ##
==========================================
+ Coverage   92.89%   92.91%   +0.02%     
==========================================
  Files          20       20              
  Lines        7595     7595              
==========================================
+ Hits         7055     7057       +2     
+ Misses        540      538       -2     

see 1 file with indirect coverage changes

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[ziao-guo]

good job! Merged.