Fix typo in example
Fix typo in example

gaearon/gitbook-plugin-prism,marcusgadbem/gitbook-plugin-anchors-wrapper,glabcn/gitbook-plugin-anchors-wrapper,genomecompilermanual/gitbook_plugin,Noamyoungerm/gitbook-plugin-base,nicgirault/gitbook-plugin-circosjs,spricity/google_code_prettify,GitbookIO/plugin,rlmv/gitbook-plugin-anchors,wabarr/plugin-wabtheme,todvora/gitbook-plugin-image-captions,gaearon/gitbook-plugin-anchors,rlmv/gitbook-plugin-include,gmassanek/gitbook-plugin-js-sequence-diagram,pm5/gitbook-plugin-lexicon,kmelve/gitbook-plugin-typekit,todvora/gitbook-plugin-image-captions