chore: remove redundant clone code (#18997)

## Which issue does this PR close?

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It's very simple, do I need to propose an issue?
- Closes #.

## Rationale for this change

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We don't need to clone `ExectuionPlan` when `repartitioned()` didn't
happened.

## What changes are included in this PR?

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Very simple, just remove extra `clone()`.

## Are these changes tested?

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Compile passed.

## Are there any user-facing changes?

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No

Signed-off-by: Smith Cruise <chendingchao1@126.com>

Author: Smith-Cruise

datafusion/datasource/src/source.rs

@@ -263,17 +263,15 @@ impl ExecutionPlan for DataSourceExec {
             self.properties().eq_properties.output_ordering(),
         )?;
 
-        if let Some(source) = data_source {
+        Ok(data_source.map(|source| {
             let output_partitioning = source.output_partitioning();
             let plan = self
                 .clone()
                 .with_data_source(source)
                 // Changing source partitioning may invalidate output partitioning. Update it also
                 .with_partitioning(output_partitioning);
-            Ok(Some(Arc::new(plan)))
-        } else {
-            Ok(Some(Arc::new(self.clone())))
-        }
+            Arc::new(plan) as _
+        }))
     }
 
     fn execute(