Perform file storage tests serialized

TrioTests/FileStorageTests.swift

@@ -3,7 +3,7 @@ import Testing
 
 @testable import Trio
 
-@Suite("File Storage Tests") struct FileStorageTests {
+@Suite("File Storage Tests", .serialized) struct FileStorageTests {
     let storage = BaseFileStorage()
 
     struct DummyObject: JSON, Equatable {

TrioTests/PluginManagerTests.swift

@@ -3,7 +3,7 @@ import Swinject
 import Testing
 @testable import Trio
 
-@Suite("Plugin Manager Tests") struct PluginManagerTests: Injectable {
+@Suite("Plugin Manager Tests", .serialized) struct PluginManagerTests: Injectable {
     let fileStorage = BaseFileStorage()
     @Injected() var pluginManager: PluginManager!
     let resolver = TrioApp().resolver