chore: update go.sum after go mod tidy

[Olexandr88]

Run go mod tidy in rlp/fuzz module to sync go.sum

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Note

Low Risk
Only updates go.sum for the rlp/fuzz module (dependency checksum metadata) with no functional code changes.

Overview
Runs go mod tidy in rlp/fuzz, updating go.sum to remove a large set of unused module checksum entries and keep only currently required dependencies.

No production code changes; this is a dependency metadata cleanup scoped to the fuzzing module.

^{Written by Cursor Bugbot for commit 1a3ff3c. This will update automatically on new commits. Configure here.}