feat(collections): do not error when iterating empty collections

[testinginprod]

Description

Closes: #17289

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[julienrbrt]

We can probably remove this now too:

cosmos-sdk/collections/genesis.go

Lines 45 to 48 in 3de7bba

	if errors.Is(err, ErrInvalidIterator) {
	_, err = io.WriteString(writer, "]")
	return err
	}

[odeke-em]

LGTM, thank you @testinginprod!