Fix non-existent artifacts_file in job api

doc/api/jobs.md

@@ -33,7 +33,6 @@ Example of response
     },
     "coverage": null,
     "created_at": "2015-12-24T15:51:21.727Z",
-    "artifacts_file": null,
     "finished_at": "2015-12-24T17:54:24.921Z",
     "artifacts_expire_at": "2016-01-23T17:54:24.921Z",
     "id": 6,
@@ -151,7 +150,6 @@ Example of response
     },
     "coverage": null,
     "created_at": "2015-12-24T15:51:21.727Z",
-    "artifacts_file": null,
     "finished_at": "2015-12-24T17:54:24.921Z",
     "artifacts_expire_at": "2016-01-23T17:54:24.921Z",
     "id": 6,
@@ -267,7 +265,6 @@ Example of response
   },
   "coverage": null,
   "created_at": "2015-12-24T15:51:21.880Z",
-  "artifacts_file": null,
   "finished_at": "2015-12-24T17:54:31.198Z",
   "artifacts_expire_at": "2016-01-23T17:54:31.198Z",
   "id": 8,
@@ -458,7 +455,6 @@ Example of response
   },
   "coverage": null,
   "created_at": "2016-01-11T10:13:33.506Z",
-  "artifacts_file": null,
   "finished_at": "2016-01-11T10:14:09.526Z",
   "id": 42,
   "name": "rubocop",
@@ -505,7 +501,6 @@ Example of response
   },
   "coverage": null,
   "created_at": "2016-01-11T10:13:33.506Z",
-  "artifacts_file": null,
   "finished_at": null,
   "id": 42,
   "name": "rubocop",
@@ -654,7 +649,6 @@ Example of response
   },
   "coverage": null,
   "created_at": "2016-01-11T10:13:33.506Z",
-  "artifacts_file": null,
   "finished_at": null,
   "id": 42,
   "name": "rubocop",