remove skillset counter entirely until it comes back as retired (#9968)

Co-authored-by: Austin Drefke <[email protected]>

Author: jadrefke

specification/search/data-plane/Azure.Search/preview/2020-06-30/searchservice.json

@@ -8488,11 +8488,6 @@
           "x-ms-client-name": "synonymMapCounter",
           "$ref": "#/definitions/ResourceCounter",
           "description": "Total number of synonym maps."
-        },
-        "skillsetCount": {
-          "x-ms-client-name": "skillsetCounter",
-          "$ref": "#/definitions/ResourceCounter",
-          "description": "Total number of skillsets."
         }
       },
       "required": [