test(bank): check that zero balances are deleted (#9559)

## Description

Ref: zero balance check for v0.43

---

### Author Checklist

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- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
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- [x] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [x] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [x] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [x] updated the relevant documentation or specification
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### Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

x/bank/keeper/keeper_test.go

@@ -443,6 +443,15 @@ func (suite *IntegrationTestSuite) TestSendCoins() {
 	acc2Balances := app.BankKeeper.GetAllBalances(ctx, addr2)
 	expected = sdk.NewCoins(newFooCoin(150), newBarCoin(75))
 	suite.Require().Equal(expected, acc2Balances)
+
+	// we sent all foo coins to acc2, so foo balance should be deleted for acc1 and bar should be still there
+	var coins []sdk.Coin
+	app.BankKeeper.IterateAccountBalances(ctx, addr1, func(c sdk.Coin) (stop bool) {
+		coins = append(coins, c)
+		return true
+	})
+	suite.Require().Len(coins, 1)
+	suite.Require().Equal(newBarCoin(25), coins[0], "expected only bar coins in the account balance, got: %v", coins)
 }
 
 func (suite *IntegrationTestSuite) TestValidateBalance() {