fix: fix naming conventions for mag pouches, remove redundant plural

[chaosvolt]

Purpose of change

Fixes some assorted things I overlooked when approving #3777

Describe the solution

1. Removes redundant, misspelled plural form of the renamed ammo satchel.
2. Renamed ammo pouches/satchels to refer to magazines instead. Turns out someone (someones, both @yay855 who PR'd it and me who approved it) forgot that "ammo satchel" was already in use for the name of the makeshift waist mag carrier, so might as well just standardize that now.

Describe alternatives you've considered

1. Reverting the ammo pouch name change in above PR.
2. Screaming.

Testing

1. Checked affected file for syntax and lint errors.
2. Used my eyes for once.

Additional context

Checklist