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/glob.rs

@@ -170,7 +170,7 @@ fn glob_files_in_parent(
         let expected = expected
             .join(" ")
             .replace('/', std::path::MAIN_SEPARATOR_STR);
-        assert_eq!(actual.out, expected, "\n  test: {}", tag);
+        assert_eq!(actual.out, expected, "\n  test: {tag}");
     });
 }