Update GHA to grab gurobipy from PyPI

[blnicho]

Summary/Motivation:

We currently grab gurobipy from pypi.gurobi.com when setting up our pip-based GHA jobs. This recently started causing test failures due to this site not being reachable. The Gurobi Python installation instructions say to grab gurobipy straight from PyPI so this PR updates our workflows to do so.

Changes proposed in this PR:

• pip install gurobipy directly from PyPI

Legal Acknowledgement

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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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.45%. Comparing base (6393961) to head (6d94224).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3254      +/-   ##
==========================================
- Coverage   88.45%   88.45%   -0.01%     
==========================================
  Files         849      849              
  Lines       95329    95329              
==========================================
- Hits        84327    84319       -8     
- Misses      11002    11010       +8     

Flag	Coverage Δ
linux	86.41% <ø> (+<0.01%)	:arrow_up:
osx	?
other	86.60% <ø> (-0.01%)	:arrow_down:
win	83.90% <ø> (-0.01%)	:arrow_down:

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[jsiirola]

Do we know why we are pinning the Gurobi version to 10.0.3?

[mrmundt]

Do we know why we are pinning the Gurobi version to 10.0.3?

Yup - see #3052