Confidence intervals of Sobol's method are wrong

[devmotion]

The confidence level conf_level of the Sobol method only shows up in https://github.com/SciML/GlobalSensitivity.jl/blob/1816f68d11e8b99d15d397c68696ea2f2955da96/src/sobol_sensitivity.jl#L299-L300 - but since alpha is not used in the further calculations, the returned confidence intervals are not affected by the conf_level setting.