STYLE.md: Fix a typo
Replace 'betwen' with 'between'.
@@ -108,7 +108,7 @@ When creating `use` statements, these statements should be divided into groups
separated by an empty line. Empty groups can be omitted altogether (i.e. no
double empty lines). Formatting imports like this allows `cargo fmt` to
sort within the groups, but the groups are always kept in the same relative
-order betwen them. The groups are, in order:
+order between them. The groups are, in order:
1. Reexports from the same crate.
2. Reexports from the `core`, `alloc` or `std`.
