Update docs for aggregate repartition test (apache#18650)

## Which issue does this PR close?
Test was updated in
https://github.com/apache/datafusion/pull/18521/files#diff-fe22c0d1093b8b848a9317b0796f58276d36b98c8444865dcc0c252fd5b02632R102
but docs don't reflect the new plan.
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- Closes #.

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Only doc changes for tests.
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Co-authored-by: Xander <xbailey@palantir.com>

Author: xanderbailey

datafusion/sqllogictest/test_files/aggregate_repartition.slt

@@ -84,9 +84,6 @@ physical_plan
 07)------------DataSourceExec: file_groups={1 group: [[WORKSPACE_ROOT/datafusion/sqllogictest/test_files/scratch/aggregate_repartition/dim.csv]]}, projection=[env], file_type=csv, has_header=true
 
 # Test 2: EXPLAIN query for Parquet table with GROUP BY
-# This plan differs from the one above and includes two consecutive repartitions — one round-robin and one hash —
-# which seems unnecessary. We may want to align it with the previous plan (push the round robin down or remove the round robin), or, if the input file is small,
-# avoid repartitioning altogether. A single partition should suffice for a single-step aggregate as the plan after this.
 
 query TT
 EXPLAIN SELECT env, count(*) FROM dim_parquet GROUP BY env;