chore: bump to v4 (#260)

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## Overview

We need to bump to v4 because we have breaking changes that we want to
release.

## Checklist

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- [ ] New and updated code has appropriate documentation
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go.mod

@@ -1,4 +1,4 @@
-module github.com/celestiaorg/blobstream-contracts/v3
+module github.com/celestiaorg/blobstream-contracts/v4
 
 go 1.21.1