Remove inappropriate dispersion_modifier fields

[ymber]

Summary

SUMMARY: Content "Remove dispersion_modifier values from gunmods that don't affect mechanical accuracy"

Purpose of change

Several gunmods that should have no effect on the maximum achievable mechanical accuracy of the weapon they are installed on were affecting that.

Describe the solution

Remove inappropriate dispersion_modifier fields.

Testing

Game loads correctly with no errors and stat impacts of gunmods are as expected.

[SirPendrak]

While removing most of theese makes sense, what about things mounted directly to the end of the barell? Like bipod in some old military rifles, or some bayonets to this day. Additional weight on barrel can affect the accuarcy badly, and mods should be mounted to guns chassis.

[ymber]

Anything that affects barrel harmonics would have some kind of impact but given how we model attachment points for these items that isn't applicable to any of them.