Reduce size of print head without fans for one-at-a-time mode

This allows you to place models more compactly.

According to the discussion at #5590, this was tested to work well.

Fixes #5590.

resources/definitions/creality_ender3.def.json

@@ -13,10 +13,10 @@
         "machine_depth": { "default_value": 220 },
         "machine_height": { "default_value": 250 },
         "machine_head_polygon": { "default_value": [
-                [-26, 34],
-                [-26, -32],
-                [22, -32],
-                [22, 34]
+                [-1, 1],
+                [-1, -1],
+                [1, -1],
+                [1, 1]
             ]
         },
         "machine_head_with_fans_polygon": { "default_value": [