Fix NSE Leak (#2022)

ElementX/Sources/Services/Media/Provider/MediaFileHandleProxy.swift

@@ -59,9 +59,13 @@ extension MediaFileHandleProxy: Hashable {
 /// An unmanaged file handle that can be created direct from a URL.
 ///
 /// This type allows for mocking but doesn't provide the automatic clean-up mechanism provided by the SDK.
-private struct UnmanagedMediaFileHandle: MediaFileHandleProtocol {
+private class UnmanagedMediaFileHandle: MediaFileHandleProtocol {
     let url: URL
     
+    init(url: URL) {
+        self.url = url
+    }
+    
     func path() -> String {
         url.path()
     }