BUG: fix get_controller_observed_variables in the air brakes examples

[Gui-FernandesBR]

Pull request type

• Code changes (bugfix, features)

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally
• CHANGELOG.md has been updated (if relevant)

Current behavior

Since this commit (4ee4c7d#diff-a2ba60171d218c6b07372fae8759f8b235b7aa40006c08afef14b96c13d37902), the method Flight.get_controller_observed_variables is no longer a cached property and therefore cannot be iterated. This generates the following error when building the documentation:

Cell raised uncaught exception:
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[5], line 5
      1 import matplotlib.pyplot as plt
      3 time_list, deployment_level_list, drag_coefficient_list = [], [], []
----> 5 for time, deployment_level, drag_coefficient in test_flight.get_controller_observed_variables:
      6     time_list.append(time)
      7     deployment_level_list.append(deployment_level)

TypeError: 'method' object is not iterable

New behavior

• Solved the problem!
• Added a test to invoke the problematic method.
• Build and checked the documentation.

Breaking change

• No

Additional information

• @phmbressan can you review this one before the ENH: update master with develop for version 1.2.0 #536 ?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (db95053) 72.46% compared to head (6fba7fb) 72.48%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #551      +/-   ##
===========================================
+ Coverage    72.46%   72.48%   +0.02%     
===========================================
  Files           59       59              
  Lines         9568     9568              
===========================================
+ Hits          6933     6935       +2     
+ Misses        2635     2633       -2     

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