fix: [vulnerability] sighting added

vulnerability/machinetag.json

@@ -2,7 +2,7 @@
   "namespace": "vulnerability",
   "expanded": "vulnerability",
   "description": "A taxonomy for describing vulnerabilities (software, hardware, or social) on different scales or with additional available information.",
-  "version": 2,
+  "version": 3,
   "predicates": [
     {
       "value": "exploitability",
@@ -16,7 +16,8 @@
       "description": "Complementary information related to the vulnerability."
     },
     {
-      "value": "Sighting",
+      "value": "sighting",
+      "expanded": "Sighting",
       "description": "Sighting information related to the vulnerability."
     }
   ],