Clarify PruneExecMeta comment

Co-authored-by: julienrbrt <29894366+julienrbrt@users.noreply.github.com>

Author: Copilot

execution/evm/execution.go

@@ -268,7 +268,7 @@ func NewEngineExecutionClient(
 
 // PruneExecMeta removes execution metadata at the given height.
 // It is used by the block pruner to delete historical exec meta entries.
-// Returns nil if no store is configured.
+// Returns a nil error if no store is configured.
 func (c *EngineClient) PruneExecMeta(ctx context.Context, height uint64) error {
 	if c.store == nil {
 		return nil