Bug fix in matrix-style tracks height computation and fixed CI

[StefanoCretti]

When using style=matrix, PlotHicMat.get_track_height still multiplied track height by 0.8. This was probably the previous way of getting a roughly equal aspect ratio of the matrix since margins were not kept into account in frame width computation. Now that frame width computation is fixed, it actually breaks the aspect ratio.

Likely caused by me forgetting to remove the multiplier when frame width computation formula was fixed.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 39.87%. Comparing base (6432254) to head (c50d509).
Report is 21 commits behind head on master.

Files with missing lines	Patch %	Lines
coolbox/core/track/hicmat/plot.py	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #105      +/-   ##
==========================================
+ Coverage   39.74%   39.87%   +0.12%     
==========================================
  Files          81       81              
  Lines        5271     5440     +169     
==========================================
+ Hits         2095     2169      +74     
- Misses       3176     3271      +95     

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[StefanoCretti]

Also fixed CI by:

• forcing sqlite installation from conda-forge when testing
• updated codecov github action (1 -> 5)
  Given the maintenance status of the repository it might be better to drop codecov altogether (to avoid bot comments in PR), but leaving it in since it was there initially.