operationId in the link object is a string

https://spec.openapis.org/oas/v3.1.0#fixed-fields-16

Author: karenetheridge

schemas/v3.1/schema.json

@@ -936,7 +936,9 @@
           "type": "string",
           "format": "uri-reference"
         },
-        "operationId": true,
+        "operationId": {
+          "type": "string"
+        },
         "parameters": {
           "$ref": "#/$defs/map-of-strings"
         },

schemas/v3.1/schema.yaml

@@ -646,7 +646,8 @@ $defs:
       operationRef:
         type: string
         format: uri-reference
-      operationId: true
+      operationId:
+        type: string
       parameters:
         $ref: '#/$defs/map-of-strings'
       requestBody: true