Fix bug in gun variant validator script

[anothersimulacrum]

Summary

None

Purpose of change

GuardianDll: ERROR: Guns colt_anaconda_8 and colt_anaconda_6 are too similar and should be combined
GuardianDll: doc: "the barrel lengths of the guns are within 2 cm"
GuardianDll: "barrel_length": "203 mm" vs "barrel_length": "153 mm"
GuardianDll: what lies? documentation, script, or common sense?
anothersimulacrum: { 'id': 'colt_anaconda_8', 'ranged_damage': -17, 'ammo': ['44'], 'volume': 1384, 'weight': 1672, 'longest_side': 350, 'dispersion': 280, 'modes': [1], 'magazines': [6], 'speedloaders': ['44_speedloader6']}
anothersimulacrum: { 'id': 'colt_anaconda_6', 'ranged_damage': -17, 'ammo': ['44'], 'volume': 1299, 'weight': 1499, 'longest_side': 300, 'dispersion': 280, 'modes': [1], 'magazines': [6], 'speedloaders': ['44_speedloader6']}
anothersimulacrum: barrel_length isn't in the scraped JSON for whatever reason

Oops.

Describe the solution

Ensure all keys are preserved for checks.

Testing

Fetch #74719 and tools/json_tools/gun_variant_validator.py -v -cin data/json exits with code 0.

Additional context