Calling submitTransaction messes up subsequent horizon calls on versions > 14.3.0

[corymsmith]

Describe the bug
After submitting a transaction the http client uses the wrong url to fetch stats.

Calling feeStats() returns this error and is calling /transactions/fee_stats

{
  response: {
    type: 'https://stellar.org/horizon-errors/bad_request',
    title: 'Bad Request',
    status: 400,
    detail: 'The request you sent was invalid in some way.',
    extras: {
      invalid_field: 'tx_id',
      reason: 'Transaction hash must be a hex-encoded, lowercase SHA-256 hash'
    }
  }
}

What version are you on?
14.3.1 and 14.3.2

To Reproduce
This script reproduces the behaviour:

const Stellar = require('@stellar/stellar-sdk');

async function createTransaction() {
  const amount = 10;
  const to = 'GDHFCOVVCWBLLJ5HFEKAPDXYMP5UIME6YVWZSTOTF3QETSCBCGNWVSGN';
  const keypair = Stellar.Keypair.fromSecret('TEST_SECRET_KEY');
  const client = new Stellar.Horizon.Server('https://horizon-testnet.stellar.org');
  const fee = (await client.feeStats()).max_fee.p70;
  const account = await client.loadAccount(keypair.publicKey());

  let stellarTx = new Stellar.TransactionBuilder(account, {
    fee,
    networkPassphrase: Stellar.Networks.TESTNET
  }).addOperation(Stellar.Operation.payment({
    asset: Stellar.Asset.native(),
    destination: to,
    amount: amount.toString()
  })).setTimeout(30).build();
  stellarTx.sign(keypair);

  // Submit the transaction to the network
  await client.submitTransaction(stellarTx);

  // Fetch fees again
  // This errors, I logged out url.toString() inside sendNormalRequest and its calling `https://horizon-testnet.stellar.org/transactions/fee_stats` instead of `https://horizon-testnet.stellar.org/fee_stats`
  const feeStats = await client.feeStats();
  console.log(feeStats);
}

createTransaction();

Expected behavior
Should call the correct endpoint.

Additional context
I tested on v14.3.0 and it works, breaks on 14.3.2 and 14.3.3