style(indexing): re-fmt parquet_merge_executor to latest nightly rustfmt

Same nightly-rustfmt drift as the storekey commit on #6424
(local nightly 2026-05-11 vs CI's 2026-05-17): the `mixed_prefix_ok`
binding and the `merge_parquet_split_metadata` call now fit
single-line under the newer width heuristics. No behaviour change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: g-talbot

quickwit/quickwit-indexing/src/actors/parquet_pipeline/parquet_merge_executor.rs

@@ -237,17 +237,13 @@ impl Handler<ParquetMergeScratch> for ParquetMergeExecutor {
         // them at read time), so the input-side equality check in
         // `merge_parquet_split_metadata` would spuriously fail. Regular
         // merges keep the strict check.
-        let mixed_prefix_ok = scratch
-            .merge_operation
-            .target_prefix_len_override
-            .is_some();
+        let mixed_prefix_ok = scratch.merge_operation.target_prefix_len_override.is_some();
 
         let mut merged_splits = Vec::with_capacity(outputs.len());
         for output in &outputs {
-            let mut metadata =
-                merge_parquet_split_metadata(input_splits, output, mixed_prefix_ok)
-                    .context("failed to build merge output metadata")
-                    .map_err(|e| ActorExitStatus::from(anyhow::anyhow!(e)))?;
+            let mut metadata = merge_parquet_split_metadata(input_splits, output, mixed_prefix_ok)
+                .context("failed to build merge output metadata")
+                .map_err(|e| ActorExitStatus::from(anyhow::anyhow!(e)))?;
 
             // Use the split ID that was assigned when the merge operation was
             // planned, rather than the one generated inside