fix typo in book example link #12

Job	Run time
Rustfmt	15s
semver	46s
Clippy	3m 54s
Build Wasm Examples (basic)	58s
Build Wasm Examples (callback-example)	59s
Code Coverage	20s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 5s
Build Book	3m 24s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	3m 8s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 18s
Build Examples (customization/consistent_static_format_export)	1m 16s
Build Examples (customization/density_mapbox_example)	44s
Build Examples (custom_controls)	33s
Build Examples (basic_charts)	34s
Build Examples (financial_charts)	34s
Build Examples (customization/multiple_plots_example)	34s
Build Examples (maps)	43s
Build Examples (images)	53s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	6m 2s
Build Examples (scientific_charts)	31s
Build Examples (ndarray)	34s
Build Examples (themes)	33s
Build Examples (kaleido)	1m 42s
Build Examples (shapes)	34s
Build Examples (statistical_charts)	38s
Build Examples (subplots)	30s
Build Examples (3d_charts)	34s
	37m 36s

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