documentation missing on sensitivity analysis functions in pypowsybl

[adeledesmoutisartelys]

Describe the current behavior

The documentation of some sensitivity analysis functions in pypowsybl is missing. The documentation currently describes functions to read sa results that are deprecated (get_reference_flows() and get_branch_flows_sensitivity_matrix() and same for AC SA functions).

Describe the expected behavior

The documentation of get_sensitivity_matrix() or get_reference_matrix() should be added.

Describe the motivation

No response

Extra Information

No response