[RTM when tests pass] fixing example model paths

[EveCharbie]

This change is 

[pariterre]

@pariterre reviewed 40 of 40 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @EveCharbie)

[pariterre]

@pariterre reviewed 3 of 3 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @EveCharbie)

[codecov]

Codecov Report

❌ Patch coverage is 34.52381% with 55 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.22%. Comparing base (0b6be62) to head (d5fd98c).
⚠️ Report is 43 commits behind head on master.

Files with missing lines	Patch %	Lines
...imal_control/double_pendulum_torque_driven_IOCP.py	14.28%	6 Missing ⚠️
...oy_examples/holonomic_constraints/two_pendulums.py	20.00%	4 Missing ⚠️
...s/holonomic_constraints/two_pendulums_algebraic.py	20.00%	4 Missing ⚠️
...es/torque_driven_ocp/example_multi_biorbd_model.py	20.00%	4 Missing ⚠️
...tim/examples/getting_started/example_multistart.py	25.00%	3 Missing ⚠️
...es/muscle_driven_ocp/muscle_excitations_tracker.py	25.00%	3 Missing ⚠️
...control/example_variational_integrator_pendulum.py	33.33%	2 Missing ⚠️
..._integrator_with_holonomic_constraints_pendulum.py	33.33%	2 Missing ⚠️
...es/feature_examples/example_multinode_objective.py	33.33%	2 Missing ⚠️
..._examples/moving_horizon_estimation/cyclic_nmpc.py	33.33%	2 Missing ⚠️
... and 17 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1029      +/-   ##
==========================================
- Coverage   77.26%   77.22%   -0.04%     
==========================================
  Files         184      184              
  Lines       20339    20383      +44     
==========================================
+ Hits        15714    15741      +27     
- Misses       4625     4642      +17     

Flag	Coverage Δ
unittests	77.22% <34.52%> (-0.04%)	⬇️

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