Update previous version URI.

Author: gkellogg

index.html

@@ -24,7 +24,7 @@
 
       // if there is a previously published draft, uncomment this and set its YYYY-MM-DD date
       // and its maturity status
-      prevVersion:          "https://www.w3.org/TR/2018/WD-json-ld11-api-20181012/",
+      prevVersion:          "https://www.w3.org/TR/2018/WD-json-ld11-api-20181214/",
       previousPublishDate:  "2018-10-12",
       previousMaturity:     "WD",
       prevRecURI:           "https://www.w3.org/TR/2014/REC-json-ld-api-20140116/",