NFC: Update URLs

[jsiirola]

Fixes # .

Summary/Motivation:

This changes two URLs in the documentation:

• Switch the URLs pointing to John CHenneck's infeasibility slides from HTTPS to HTTP due to a truse issue with the carelton.ca SSL certificate
• Switch the merged PRs badge color from yellow to green (to match the convention that green badges are "good" and yellow/red are indicating problems)

Changes proposed in this PR:

• Update URL to http://www.sce.carleton.ca/faculty/chinneck/docs/CPAIOR07InfeasibilityTutorial.pdf
• Change mergedPRs badge color on README.md

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.42%. Comparing base (dcaba42) to head (11b4992).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3796      +/-   ##
==========================================
- Coverage   89.42%   88.42%   -1.00%     
==========================================
  Files         909      909              
  Lines      105579   105579              
==========================================
- Hits        94411    93359    -1052     
- Misses      11168    12220    +1052     

Flag	Coverage Δ
builders	29.11% <ø> (-0.01%)	⬇️
default	86.04% <ø> (?)
expensive	35.76% <ø> (?)
linux	85.72% <ø> (-3.47%)	⬇️
linux_other	85.72% <ø> (-1.01%)	⬇️
osx	?
win	84.99% <ø> (ø)
win_other	84.99% <ø> (ø)

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