Fix content-type of put_geoip_database.json (#2864)

Author: pquentin

output/schema/schema.json

@@ -7,7 +7,8 @@
     "stability": "stable",
     "visibility": "public",
     "headers": {
-      "accept": ["application/json"]
+      "accept": ["application/json"],
+      "content_type": ["application/json"]
     },
     "url": {
       "paths": [