fix: Replace new Locker instance creation with Get method

[MS-crew]

Description

Describe the changes
[2026-03-17 02:37:26.739 +03:00] [STDOUT] ArgumentException: An item with the same key has already been added. Key: Scp1344PedestalStructure Variant(Clone) (MapGeneration.Distributors.PedestalScpLocker)
[2026-03-17 02:37:26.739 +03:00] [STDOUT] at System.Collections.Generic.Dictionary2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) [0x0015a] in <13c0c460649d4ce49f991e2c222fa635>:0 [2026-03-17 02:37:26.739 +03:00] [STDOUT] at System.Collections.Generic.Dictionary2[TKey,TValue].Add (TKey key, TValue value) [0x00000] in <13c0c460649d4ce49f991e2c222fa635>:0
[2026-03-17 02:37:26.740 +03:00] [STDOUT] at Exiled.API.Features.Lockers.Locker..ctor (MapGeneration.Distributors.Locker locker) [0x00019] in <5824ee89dbbc4693a659efef2f01ee35>:0
[2026-03-17 02:37:26.740 +03:00] [STDOUT] at (wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.MapGeneration.Distributors.SpawnableStructure.Start_Patch1(MapGeneration.Distributors.SpawnableStructure)

What is the current behavior? (You can also link to an open issue here)

What is the new behavior? (if this is a feature change)

Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

Other information:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentations

Submission checklist

• I have checked the project can be compiled
• I have tested my changes and it worked as expected

Patches (if there are any changes related to Harmony patches)

• I have checked no IL patching errors in the console

Other

• Still requires more testing