docs: Update highlight.js example to latest version
docs: Update highlight.js example to latest version

Highlight.js has evolved quite a bit since it this doc was written. Updating the example to the latest 9.6 version of Highlight JS hosted by cloudflare

gohugoio/hugo,digitalcraftsman/hugo,digitalcraftsman/hugo,mitchchn/hugo,Zenithar/hugo,fedelibre/hugo,mdhender/hugo,mdhender/hugo,Zenithar/hugo,anthonyfok/hugo,fedelibre/hugo,mdhender/hugo,jygastaud/hugo,MarkDBlackwell/hugo,bogem/hugo,tubo028/hugo,bogem/hugo,mitchchn/hugo,jygastaud/hugo,anthonyfok/hugo,mayah/hugo,mdhender/hugo,MarkDBlackwell/hugo,gohugoio/hugo,tubo028/hugo,mayah/hugo,gohugoio/hugo,fedelibre/hugo,anthonyfok/hugo,fedelibre/hugo