Fixes Erroneous Approval Error (#1125)

## Motivation

We were erroneously blocking you from calling `approve()` with too low
of a balance. This doesn't reflect how things work on chain.

## Solution

Remove that check

integration-tests/ccip-tests/actions/ccip_helpers.go

@@ -402,7 +402,8 @@ func (ccipModule *CCIPCommon) ApproveTokens() error {
 			return fmt.Errorf("failed to get allowance for token %s: %w", token.ContractAddress.Hex(), err)
 		}
 		if allowance.Cmp(ApprovedAmountToRouter) < 0 {
-			err := token.Approve(ccipModule.ChainClient.GetDefaultWallet(), ccipModule.Router.Address(), ApprovedAmountToRouter)
+			allowanceApprovalDelta := new(big.Int).Sub(ApprovedAmountToRouter, allowance)
+			err := token.Approve(ccipModule.ChainClient.GetDefaultWallet(), ccipModule.Router.Address(), allowanceApprovalDelta)
 			if err != nil {
 				return fmt.Errorf("failed to approve token %s: %w", token.ContractAddress.Hex(), err)
 			}

integration-tests/ccip-tests/contracts/contract_models.go

@@ -271,9 +271,6 @@ func (token *ERC20Token) Approve(onBehalf *blockchain.EthereumWallet, spender st
 	if err != nil {
 		return fmt.Errorf("failed to get balance of onBehalf: %w", err)
 	}
-	if onBehalfBalance.Cmp(amount) < 0 {
-		return fmt.Errorf("onBehalf '%s' does not have enough balance to approve", onBehalf.Address())
-	}
 	currentAllowance, err := token.Allowance(onBehalf.Address(), spender)
 	if err != nil {
 		return fmt.Errorf("failed to get current allowance for '%s' on behalf of '%s': %w", spender, onBehalf.Address(), err)