RFC 7946 was officially published in August 2016, i.e. before Leaflet version 1.0.0 (Sep 2016). The previous GeoJSON spec website (geojson.org) displays a big "obsolete" disclaimer on it, making it confusing for developers which version they should refer to. Replace the link to use the RFC that was in use at that time, on all HTML docs since it was available, i.e. from Leaflet 1.0.0.
* Use openstreetmap.org, not osm.org
osm.org is a convenience redirect for typing into your browser URL bar, and not an officially supported services endpoint (for example, it doesn't have the SSL certificates you might otherwise expect)
* Update reference-1.0.2.html
* Update TileLayer.js