Fix StandardSongControl.IsPaused

[qe201020335]

On 1.40.0 (maybe before as well, did not test), using the F2 pause feature will cause an uncaught exception.
Given the exception is thrown in the StandardSongControl implementation of ISongControl, any mods that access ISongControl.IsPaused in singleplayer will also be affected.
This pr fixes it.

[CRITICAL @ 23:58:11 | UnityEngine] ArgumentException: Field '_paused' not of type System.Boolean
[CRITICAL @ 23:58:11 | UnityEngine] IPA.Utilities.FieldAccessor`2[T,U].MakeAccessor (System.String fieldName) (at D:/a/BeatSaber-IPA-Reloaded/BeatSaber-IPA-Reloaded/IPA.Loader/Utilities/Accessor.cs:51)
[CRITICAL @ 23:58:11 | UnityEngine] IPA.Utilities.Async.SingleCreationValueCache`2[TKey,TValue].GetOrAdd (TKey key, System.Func`2[T,TResult] creator) (at D:/a/BeatSaber-IPA-Reloaded/BeatSaber-IPA-Reloaded/IPA.Loader/Utilities/Async/SingleCreationValueCache.cs:156)
[CRITICAL @ 23:58:11 | UnityEngine] IPA.Utilities.FieldAccessor`2[T,U].GetAccessor (System.String name) (at D:/a/BeatSaber-IPA-Reloaded/BeatSaber-IPA-Reloaded/IPA.Loader/Utilities/Accessor.cs:64)
[CRITICAL @ 23:58:11 | UnityEngine] IPA.Utilities.FieldAccessor`2[T,U].Access (T& obj, System.String name) (at D:/a/BeatSaber-IPA-Reloaded/BeatSaber-IPA-Reloaded/IPA.Loader/Utilities/Accessor.cs:74)
[CRITICAL @ 23:58:11 | UnityEngine] IPA.Utilities.FieldAccessor`2[T,U].Get (T& obj, System.String name) (at D:/a/BeatSaber-IPA-Reloaded/BeatSaber-IPA-Reloaded/IPA.Loader/Utilities/Accessor.cs:89)
[CRITICAL @ 23:58:11 | UnityEngine] IPA.Utilities.ReflectionUtil.GetField[U,T] (T obj, System.String fieldName) (at D:/a/BeatSaber-IPA-Reloaded/BeatSaber-IPA-Reloaded/IPA.Loader/Utilities/ReflectionUtil.cs:40)
[CRITICAL @ 23:58:11 | UnityEngine] SiraUtil.Tools.SongControl.StandardSongControl.get_IsPaused () (at /_/SiraUtil/Tools/SongControl/StandardSongControl.cs:14)
[CRITICAL @ 23:58:11 | UnityEngine] SiraUtil.Tools.SongControl.SongControlManager.Tick () (at /_/SiraUtil/Tools/SongControl/SongControlManager.cs:25)
[CRITICAL @ 23:58:11 | UnityEngine] Zenject.TickablesTaskUpdater.UpdateItem (Zenject.ITickable task) (at <216eee2c32db494ab39896d41fcc4e32>:0)
[CRITICAL @ 23:58:11 | UnityEngine] Zenject.TaskUpdater`1[TTask].UpdateRange (System.Int32 minPriority, System.Int32 maxPriority) (at <216eee2c32db494ab39896d41fcc4e32>:0)
[CRITICAL @ 23:58:11 | UnityEngine] Zenject.TaskUpdater`1[TTask].UpdateAll () (at <216eee2c32db494ab39896d41fcc4e32>:0)
[CRITICAL @ 23:58:11 | UnityEngine] Zenject.TickableManager.Update () (at <216eee2c32db494ab39896d41fcc4e32>:0)
[CRITICAL @ 23:58:11 | UnityEngine] Zenject.MonoKernel.Update () (at <216eee2c32db494ab39896d41fcc4e32>:0)