clarify comment

ykrt/src/compile/jitc_yk/codegen/abs_stack.rs

@@ -4,8 +4,8 @@
 /// generation. The abstract stack pointer is zero-based, so the stack pointer value also serves as
 /// the size of the stack.
 ///
-/// The implementation is platform agnostic: as the stack gets bigger, the stack pointer grows
-/// upwards, even on architectures where the stack grows downwards.
+/// The implementation is platform agnostic: as the abstract stack gets bigger, the abstract stack
+/// pointer grows upwards, even on architectures where the stack grows downwards.
 #[derive(Debug, Default)]
 pub(crate) struct AbstractStack(usize);