Fix more Release build warnings

Not being able to build locally in release mode because of the .NET 8 RC SDK is painful

src/Tgstation.Server.Host/Components/Deployment/SymlinkDmbProvider.cs

@@ -1,5 +1,4 @@
-using System.Runtime.Versioning;
-using System.Threading;
+using System.Threading;
 using System.Threading.Tasks;
 
 using Tgstation.Server.Host.IO;
@@ -9,7 +8,6 @@ namespace Tgstation.Server.Host.Components.Deployment
 	/// <summary>
 	/// A <see cref="IDmbProvider"/> that uses symlinks.
 	/// </summary>
-	[SupportedOSPlatform("windows")]
 	sealed class SymlinkDmbProvider : SwappableDmbProvider
 	{
 		/// <summary>

src/Tgstation.Server.Host/Components/Watchdog/WindowsWatchdog.cs

@@ -1,5 +1,4 @@
-using System.Runtime.Versioning;
-using System.Threading;
+using System.Threading;
 using System.Threading.Tasks;
 
 using Microsoft.Extensions.Logging;
@@ -20,7 +19,6 @@ namespace Tgstation.Server.Host.Components.Watchdog
 	/// <summary>
 	/// A variant of the <see cref="AdvancedWatchdog"/> that works on Windows systems.
 	/// </summary>
-	[SupportedOSPlatform("windows")]
 	sealed class WindowsWatchdog : AdvancedWatchdog
 	{
 		/// <summary>

src/Tgstation.Server.Host/Components/Watchdog/WindowsWatchdogFactory.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Runtime.Versioning;
 
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
@@ -21,7 +20,6 @@ namespace Tgstation.Server.Host.Components.Watchdog
 	/// <summary>
 	/// <see cref="IWatchdogFactory"/> for creating <see cref="AdvancedWatchdog"/>s.
 	/// </summary>
-	[SupportedOSPlatform("windows")]
 	class WindowsWatchdogFactory : WatchdogFactory
 	{
 		/// <summary>