Make machine check image optional (SchemaStore#4993)

Author: inverted-capital

src/schemas/json/fly.json

@@ -204,13 +204,7 @@
                 "pattern": "^\\d+s$"
               }
             },
-            "required": [
-              "command",
-              "entrypoint",
-              "image",
-              "kill_signal",
-              "kill_timeout"
-            ]
+            "required": ["command", "entrypoint", "kill_signal", "kill_timeout"]
           }
         },
         "tcp_checks": {