Remove evidence

Remove proposed term from v2 context

Addresses #1090

Author: OR13

contexts/credentials/v2

@@ -29,10 +29,6 @@
         "description": {
           "@id": "https://schema.org/description"
         },
-        "evidence": {
-          "@id": "https://www.w3.org/2018/credentials#evidence",
-          "@type": "@id"
-        },
         "validFrom": {
           "@id": "https://www.w3.org/2018/credentials#validFrom",
           "@type": "http://www.w3.org/2001/XMLSchema#dateTime"