Fix steel_lump volume

[cake-pie]

Summary

SUMMARY: Content "fix steel_lump volume"

Purpose of change

Bring stats of "lump of steel" steel_lump in line with "chunk of steel" and "scrap metal".

Thanks to helpful comments in metals.json showing the math, it is clear that there was a mistake in the volume for steel_lump.

    "id": "scrap",
    "name": "scrap metal",
    "weight": 50,
    "volume": 1,
    "count": 2,
    "stack_size": 10, "//": "Density 7.60g/cm³ ~ 1.9kg/250ml @ 50g/unit ~ stack 40 but fragments stacks poorly so only 25% of this",

In-game, scrap metal (10) is 500g/250ml which is approx 25% as heavy as the quoted 1.9kg/250ml of a solid block of steel.

    "id": "steel_chunk",
    "name": "chunk of steel",
    "weight": 250,
    "volume": 1,
    "stack_size": 4, "//": "Density 7.60g/cm³ ~ 1.9kg/250ml @ 250g/unit ~ stack 8 but mishapen so only 50% of this",

In-game, chunk of steel (4) is 1kg/250ml which is approx 50% as heavy as the quoted 1.9kg/250ml of a solid block of steel.

    "id": "steel_lump",
    "name": "lump of steel",
    "weight": 1000,
    "volume": 2,
    "stack_size": 2, "//": "Density 7.60g/cm³ ~ 1.9kg/250ml @ 1000g/unit ~ stack 2 and formed as a solid ingot so 100% of this",

In-game, lump of steel (1) is 1kg/250ml which is not the expected 100% density given by the comment.

Describe the solution

Change the volume of "lump of steel" steel_lump in /items/resources/metals.json
"volume": 2,
"volume": 1,
This gives lump of steel (2) at 2kg/250ml which is what we'd expect.