Fix easy clippy lints from latest stable (#16053)

1.88.0 was released today, clippy now lints (machine-applicable)
against:
- format strings with empty braces that could be inlined
  - easy win
- `manual_abs_diff`
- returning of a stored result of the last expression.
  - this can be somewhat contentious but touched only a few places

crates/nu-command/tests/commands/table.rs

@@ -3698,11 +3698,10 @@ fn table_footer_inheritance() {
         field0: [ [ y1, y2, y3 ]; [ 1 2 3 ] [ 79 79 79 ] [ {{ f1: 'a string', f2: 1000 }}, 1, 2 ] ],\
         field1: [ a, b, c ],\
         field2: [ 123, 234, 345 ],\
-        field3: {},\
+        field3: {table1},\
         field4: {{ f1: 1, f2: 3, f3: {{ f1: f1, f2: f2, f3: f3 }} }},\
         field5: [ [ x1, x2, x3 ]; [ 1 2 3 ] [ 79 79 79 ] [ {{ f1: 'a string', f2: 1000 }}, 1, 2 ] ],\
-    }}",
-        table1
+    }}"
     );
     let actual = nu!(format!(
         "$env.config.table.footer_inheritance = true; {structure} | table --width=80 --expand"