fix : snapshot to the modern multiline format (#19517)

## Which issue does this PR close?
N/A

## Rationale for this change
A legacy inline insta snapshot was using an outdated format that does
not start and end with a newline. Newer versions of insta warn about
this format and will fail to match such snapshots in the future.
Updating the snapshot to the modern multiline format ensures forward
compatibility and avoids future snapshot failures.

## What changes are included in this PR?

- Converted a legacy inline insta snapshot to the modern multiline raw
snapshot format.
- Added leading and trailing newlines as required by current insta
snapshot conventions.
- No changes were made to the underlying logic or behavior.


## Are these changes tested?
Yes

## Are there any user-facing changes?
No

Author: Nachiket-Roy

datafusion/sql/tests/sql_integration.rs

@@ -4508,7 +4508,10 @@ fn test_parse_escaped_string_literal_value() {
     let plan = logical_plan(sql).unwrap();
     assert_snapshot!(
         plan,
-        @"Projection: character_length(Utf8(\"%\")) AS len, Utf8(\"K\") AS hex, Utf8(\"\u{1}\") AS unicode\n  EmptyRelation: rows=1"
+        @r#"
+    Projection: character_length(Utf8("%")) AS len, Utf8("K") AS hex, Utf8("
") AS unicode
+      EmptyRelation: rows=1
+    "#
     );
 
     let sql = r"SELECT character_length(E'\000') AS len";