Remove open_container:true from cans

This makes cans behave like other food/beverage containers (water
bottles, glass bottles and jars etc.),  as if the cans had lids.  Not
very realistic, but perhaps more credible than all factory-sealed cans
leaking as soon as they are picked up.

In other words this allows refilling empty cans, and still be able to
carry them without spilling, since the "spillable" status of an empty
can is no longer present.

data/json/items/containers.json

@@ -572,7 +572,6 @@
         "pocket_type": "CONTAINER",
         "rigid": true,
         "watertight": true,
-        "open_container": true,
         "max_contains_volume": "250 ml",
         "max_contains_weight": "1 kg",
         "sealed_data": { "spoil_multiplier": 0.0 }
@@ -668,7 +667,6 @@
         "pocket_type": "CONTAINER",
         "rigid": true,
         "watertight": true,
-        "open_container": true,
         "max_contains_volume": "250 ml",
         "max_contains_weight": "1 kg",
         "sealed_data": { "spoil_multiplier": 0.0 }
@@ -700,7 +698,6 @@
         "pocket_type": "CONTAINER",
         "rigid": true,
         "watertight": true,
-        "open_container": true,
         "max_contains_volume": "500 ml",
         "max_contains_weight": "2 kg",
         "sealed_data": { "spoil_multiplier": 0.0 }