Update rand_distr requirement from 0.5 to 0.6 #144

Job	Run time
Build Wasm Examples (callback-example)	58s
Code Coverage	9s
Clippy	4m 52s
Build Wasm Examples (basic)	1m 4s
semver	45s
Rustfmt	14s
Build Book	3m 56s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	2m 56s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 32s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	5m 25s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	7m 10s
Build Examples (3d_charts)	32s
Build Examples (customization/density_mapbox_example)	29s
Build Examples (custom_controls)	35s
Build Examples (kaleido)	1m 30s
Build Examples (themes)	32s
Build Examples (subplots)	31s
Build Examples (images)	45s
Build Examples (statistical_charts)	36s
Build Examples (basic_charts)	27s
Build Examples (maps)	47s
Build Examples (shapes)	35s
Build Examples (customization/consistent_static_format_export)	1m 42s
Build Examples (ndarray)	31s
Build Examples (financial_charts)	37s
Build Examples (scientific_charts)	25s
Build Examples (customization/multiple_plots_example)	30s
	42m 5s

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