Removed Duplicate Using. Removed Unused Using. (#2163)

# Description

Removed duplicate using statements, removed unused using statements.
this will decrease the number of warnings a small bit, and decrease
unused dependency references in general.
---

# TODO

- [x] Remove double references.
- [x] Remove unused references.
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# Changelog

🆑
- remove: double references in code
- remove: unused references in code that had double references.

Co-authored-by: ilmenwe <no@mail.com>

(cherry picked from commit 9b73c88feefff68223f083893505826dc021ddee)

Content.Server/Explosion/EntitySystems/ExplosionSystem.Processing.cs

@@ -17,9 +17,6 @@ using Robust.Shared.Random;
 using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 using TimedDespawnComponent = Robust.Shared.Spawners.TimedDespawnComponent;
-using Content.Server.Atmos.Components;
-using Content.Server.Atmos.EntitySystems;
-
 namespace Content.Server.Explosion.EntitySystems;
 
 public sealed partial class ExplosionSystem