rust: fmt: Fix grammar in Adapter description

Add a missing `and` in the description of the `Adapter`.

Fixes: c5cf01b ("rust: support formatting of foreign types")
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Acked-by: Tamir Duberstein <tamird@gmail.com>
Link: https://patch.msgid.link/20260102084821.1077864-1-dirk.behme@de.bosch.com
[ Reworded for typo. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: dirkbehme

rust/kernel/fmt.rs

@@ -6,7 +6,7 @@
 
 pub use core::fmt::{Arguments, Debug, Error, Formatter, Result, Write};
 
-/// Internal adapter used to route allow implementations of formatting traits for foreign types.
+/// Internal adapter used to route and allow implementations of formatting traits for foreign types.
 ///
 /// It is inserted automatically by the [`fmt!`] macro and is not meant to be used directly.
 ///