refactor(firestore): update pipeline expressions test to use arraySlice and remove unused expressions

Author: SelaseKay

packages/cloud_firestore/cloud_firestore/pipeline_example/integration_test/pipeline/pipeline_expressions_e2e.dart

@@ -821,26 +821,15 @@ void runPipelineExpressionsTests() {
     });
 
     test(
-      'addFields with new array pipeline expressions returns values',
+      'addFields with arraySlice returns sliced array',
       () async {
-        final value = Expression.variable('value');
-        final index = Expression.variable('index');
         final snapshot = await firestore
             .pipeline()
             .collection('pipeline-e2e')
             .where(Expression.field('test').equalValue('expressions'))
             .where(Expression.field('score').equalValue(50))
             .addFields(
               Expression.field('arr').arraySlice(1, 2).as('arr_slice'),
-              Expression.field('arr')
-                  .arrayFilter('value', value.greaterThanValue(3))
-                  .as('arr_filtered'),
-              Expression.field('arr')
-                  .arrayTransform('value', value.multiplyValue(10))
-                  .as('arr_transformed'),
-              Expression.field('arr')
-                  .arrayTransformWithIndex('value', 'index', value.add(index))
-                  .as('arr_with_index'),
             )
             .limit(1)
             .execute();
@@ -849,9 +838,6 @@ void runPipelineExpressionsTests() {
         expectResultsData(snapshot, [
           {
             'arr_slice': [4, 6],
-            'arr_filtered': [4, 6],
-            'arr_transformed': [20, 40, 60],
-            'arr_with_index': [2, 5, 8],
           },
         ]);
       },