No Bug: Fix for bad access crash causing flakey test (#8684)

Fix for bad access crash when accessing non-thread safe dict from background thread. Resolves flakey `SelectAccountTokenStoreTests` unit test test.

Sources/BraveWallet/Crypto/Stores/SelectAccountTokenStore.swift

@@ -324,7 +324,7 @@ class SelectAccountTokenStore: ObservableObject, WalletObserverStore {
               return nil
             }
             var price: String?
-            if let tokenPrice = pricesForTokensCache[token.assetRatioId.lowercased()],
+            if let tokenPrice = pricesCache[token.assetRatioId.lowercased()],
                balance > 0 {
               price = currencyFormatter.string(from: NSNumber(value: (Double(tokenPrice) ?? 0) * balance))
             }