Fix tutorial to use the correct squared slowness and remove JUDI4Flux info

[ziyiyin97]

https://github.com/slimgroup/JUDI.jl/blob/master/examples/notebooks/01_intro.ipynb contains a mistake where it uses compressional wavespeed vp to construct a model instead of squared slowness m. Fixed in this PR. Also update the wordings a bit since https://github.com/slimgroup/JUDI4Flux.jl is deprecated.

[mloubout]

Hum looks like CI is broken because of my changes to SegyIO will look into it and fix

[codecov]

Codecov Report

Base: 81.83% // Head: 81.83% // No change to project coverage 👍

Coverage data is based on head (9530bb9) compared to base (9530bb9).
Patch has no changes to coverable lines.

❗ Current head 9530bb9 differs from pull request most recent head c8f9f56. Consider uploading reports for the commit c8f9f56 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #162   +/-   ##
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  Coverage   81.83%   81.83%           
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  Files          28       28           
  Lines        2186     2186           
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  Hits         1789     1789           
  Misses        397      397           

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