Unused code in record.go

[konnov]

Surfaced from @informalsystems audit at hash da54c8d

The following code computes output hashes that are never used later in the code:

provenance/x/metadata/keeper/record.go

Lines 154 to 160 in da54c8d

	// Get the existing output hashes as both a slice and a map counting occurrences.
	existingOutputHashes := make([]string, len(existing.Outputs))
	existingOutputHashMap := map[string]int{}
	for i, o := range existing.Outputs {
	existingOutputHashes[i] = o.Hash
	existingOutputHashMap[o.Hash]++
	}

We recommend removing the unused code.