loosen type on link facet type

The rational here is we may also use these for internal links, or things
like that, which would make them not full uris.

lexicons/src/facet.ts

···
       "Facet feature for a URL. The text URL may have been simplified or truncated, but the facet reference should be a complete URL.",
     required: ["uri"],
     properties: {
-      uri: { type: "string", format: "uri" },
+      uri: { type: "string" },
     },
   },
   code: {