Confidence intervals of Sobol's method are wrong

[devmotion]

The confidence level conf_level of the Sobol method only shows up in

GlobalSensitivity.jl/src/sobol_sensitivity.jl

Lines 299 to 300 in 1816f68

	alpha = (1 - method.conf_level)
	std(x, mean = mean) / sqrt(length(x))

- but since alpha is not used in the further calculations, the returned confidence intervals are not affected by the conf_level setting.