docs: update broken source URLs in dataset metadata#728

dsmedia merged 7 commits intovega:mainvega/vega-datasets:mainfrom

dsmedia:claude/fix-dataset-source-urls-011CUWvJQkDNwVpAv1r8MCXSdsmedia/vega-datasets:claude/fix-dataset-source-urls-011CUWvJQkDNwVpAv1r8MCXSCopy head branch name to clipboard