fix: make iteration loops for simplified train consistent

[olelod]

Why is this pull request needed?

ecalc/src/libecalc/core/models/compressor/train/simplified_train.py

Line 481 in 883b7e6

def calculate_maximum_rate_given_outlet_pressure_single_calculation_point(

and

ecalc/src/libecalc/core/models/compressor/train/utils/enthalpy_calculations.py

Line 20 in 883b7e6

def calculate_enthalpy_change_head_iteration(

both have the same iterative loop changing z and kappa, but the algorithm for finding the max rate has an extra update in the end (

ecalc/src/libecalc/core/models/compressor/train/simplified_train.py

Line 563 in 883b7e6

maximum_actual_volume_rate = maximum_rate_function(

). Removing this extra update solves the numerical problems reported in this issue.

Issues related to this change:

ECALC 381

[olelod]

The iteration loop stops when the change in actual rate less than 0.1% from one iteration to the next. This PR basically removes the next update here. In the time step that changed here, the change was 0.09% when the iteration stops - the change in the next step (which is now removed for consistency) is 0.017%. For all other time steps the change in actual rate when the iterations stops are much less than 0.1%, and no visible difference in the test.