Manually enable the event cache as the default enabling hasn't made it to the RustSDK yet 🤦‍♂️

- https://github.com/matrix-org/matrix-rust-sdk/pull/4308

ElementX/Sources/Other/Extensions/ClientBuilder.swift

@@ -22,6 +22,7 @@ extension ClientBuilder {
             .setSessionDelegate(sessionDelegate: sessionDelegate)
             .userAgent(userAgent: UserAgentBuilder.makeASCIIUserAgent())
             .requestConfig(config: .init(retryLimit: 0, timeout: 30000, maxConcurrentRequests: nil, retryTimeout: nil))
+            .useEventCachePersistentStorage(value: true)
         
         builder = switch slidingSync {
         case .restored: builder