alloc: fix doc syntax

card10-alloc/src/lib.rs

@@ -2,7 +2,7 @@
 //!
 //! Reproduces l0dable hardware.c's `_sbrk()`
 //!
-//! Unfortunately, we cannot link _sbrk()` directly because it
+//! Unfortunately, we cannot link `_sbrk()` directly because it
 //! references the unwieldy `errno`.
 //!
 //! ## Example