Deprecate plot_{binary/multiclass}_reliability_diagram_gaps

[perellonieto]

Currently the new implementation plot_reliability_diagram accepts the binary and multiclass case with the option to show bars and gaps. Once we are happy with the new functions we need to remove the following functions

• plot_binary_reliability_diagram_gaps: https://github.com/perellonieto/PyCalib/blob/master/pycalib/visualisations/__init__.py#L246
• plot_multiclass_reliability_diagram_gaps: https://github.com/perellonieto/PyCalib/blob/master/pycalib/visualisations/__init__.py#L338