Update macros.rs
typo fix
///
/// In Postgres and MySQL you may also use `IS [NOT] DISTINCT FROM` to compare with a possibly
/// `NULL` value. In MySQL `IS NOT DISTINCT FROM` can be shortened to `<=>`.
-/// In SQLite you can us `IS` or `IS NOT`. Note that operator precedence may be different.
+/// In SQLite you can use `IS` or `IS NOT`. Note that operator precedence may be different.
///
/// ## Nullability: Output Columns
/// In most cases, the database engine can tell us whether or not a column may be `NULL`, and
