Fix fmt and test

Author: AdamGS

datafusion/physical-plan/src/sorts/sort_preserving_merge.rs

@@ -204,6 +204,7 @@ impl DisplayAs for SortPreservingMergeExec {
                         write!(f, ", ")?;
                     }
                 }
+                writeln!(f)?;
                 if let Some(fetch) = self.fetch {
                     writeln!(f, "limit={fetch}")?;
                 };

datafusion/sqllogictest/test_files/explain_tree.slt

@@ -1696,10 +1696,10 @@ physical_plan
 01)┌───────────────────────────┐
 02)│  SortPreservingMergeExec  │
 03)│    --------------------   │
-04)│   ticker ASC NULLS LAST,  │
-05)│       time ASC NULLS      │
-06)│         LASTlimit:        │
-07)│             5             │
+04)│          limit: 5         │
+05)│                           │
+06)│   ticker ASC NULLS LAST,  │
+07)│     time ASC NULLS LAST   │
 08)└─────────────┬─────────────┘
 09)┌─────────────┴─────────────┐
 10)│    CoalesceBatchesExec    │