[core] codegen: Remove obsolete comments

Comments regarding the need for `llvm.stack{save,restore}` is obsolete
now that `NDIter::indices` is allocated at the beginning of the
function.

nac3core/src/codegen/types/ndarray/nditer.rs

@@ -163,11 +163,6 @@ impl<'ctx> NDIterType<'ctx> {
     }
 
     /// Allocate an [`NDIter`] that iterates through the given `ndarray`.
-    ///
-    /// Note: This function allocates an array on the stack at the current builder location, which
-    /// may lead to stack explosion if called in a hot loop. Therefore, callers are recommended to
-    /// call `llvm.stacksave` before calling this function and call `llvm.stackrestore` after the
-    /// [`NDIter`] is no longer needed.
     #[must_use]
     pub fn construct<G: CodeGenerator + ?Sized>(
         &self,

nac3core/src/codegen/values/ndarray/nditer.rs

@@ -137,10 +137,6 @@ impl<'ctx> NDArrayValue<'ctx> {
     ///
     /// `body` has access to [`BreakContinueHooks`] to short-circuit and [`NDIterValue`] to
     /// get properties of the current iteration (e.g., the current element, indices, etc.)
-    ///
-    /// Note: The caller is recommended to call `llvm.stacksave` and `llvm.stackrestore` before and
-    /// after invoking this function respectively. See [`NDIterType::construct`] for an explanation
-    /// on why this is suggested.
     pub fn foreach<'a, G, F>(
         &self,
         generator: &mut G,