build(deps): bump github.com/ipfs/go-merkledag in /go

Bumps [github.com/ipfs/go-merkledag](https://github.com/ipfs/go-merkledag) from 0.6.0 to 0.8.1.
- [Release notes](https://github.com/ipfs/go-merkledag/releases)
- [Commits](ipfs/go-merkledag@v0.6.0...v0.8.1)

---
updated-dependencies:
- dependency-name: github.com/ipfs/go-merkledag
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

go/go.mod

@@ -109,7 +109,7 @@ require (
 	github.com/ipfs/go-ipns v0.3.0 // indirect
 	github.com/ipfs/go-log v1.0.5 // indirect
 	github.com/ipfs/go-log/v2 v2.5.1 // indirect
-	github.com/ipfs/go-merkledag v0.6.0 // indirect
+	github.com/ipfs/go-merkledag v0.8.1 // indirect
 	github.com/ipfs/go-metrics-interface v0.0.1 // indirect
 	github.com/ipfs/go-mfs v0.2.1 // indirect
 	github.com/ipfs/go-namesys v0.5.0 // indirect