fix: remove duplicate task variable

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Co-authored-by: eleanorjboyd <26030610+eleanorjboyd@users.noreply.github.com>

Author: Copilot

src/test/features/execution/runAsTask.unit.test.ts

@@ -154,7 +154,6 @@ suite('runAsTask Tests', () => {
 
             assert.strictEqual(result, mockTaskExecution, 'Should return the task execution result');
 
-            const taskArg = mockExecuteTask.firstCall.args[0] as Task;
             const execution = taskArg.execution as ShellExecution;
 
             assert.strictEqual(execution.command, 'uv', 'Should execute uv when uv mode is enabled');