[MCPE-178691] Entities with "has_gravity":false, can start floating upwards when pushed by water

Entities with a "minecraft:physics" component, that have "has_gravity" set to false can lead to the entity flying up into the air when pushed by water.

This isn't caused by the entity receiving suffocation damage. The issue doesn't happen if the collision box is larger than 1.

Reproduction steps:

Enter the attached world
Create a 1x2 hole in the ground
Place water next to the hole, on the short side
Place the entity in the water
See the entity float along the water and fly up when it hits the wall

 {
    "format_version": "1.16.0",
    "minecraft:entity": {
        "description": {
            "identifier": "test:cube",
            "is_spawnable": true,
            "is_summonable": true,
            "is_experimental": false
        },
        "components": {
            "minecraft:physics": {
                "has_collision": true,
                "has_gravity": false
            },
            "minecraft:collision_box": {
                "width": 1,
                "height": 1
            },
            "minecraft:health": {
                "min": 1,
                "value": 100,
                "max": 100
            }
        }
    }
}