Apply suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: vchuravy

src/nditeration.jl

@@ -88,7 +88,9 @@ end
 Assume that the condition `cond` is true. This is a hint to the compiler, possibly enabling
 it to optimize more aggressively.
 """
-@inline assume(cond::Bool) = Base.llvmcall(("""
+@inline assume(cond::Bool) = Base.llvmcall(
+    (
+        """
         declare void @llvm.assume(i1)
 
         define void @entry(i8) #0 {
@@ -97,9 +99,11 @@ it to optimize more aggressively.
             ret void
         }
 
-        attributes #0 = { alwaysinline }""", "entry"),
-    Nothing, Tuple{Bool}, cond)
-
+        attributes #0 = { alwaysinline }""", "entry",
+    ),
+    Nothing, Tuple{Bool}, cond
+)
+    return ntuple(Val(ndims(CI))) do I
 @inline function assume_nonzero(CI::CartesianIndices)
     ntuple(Val(ndims(CI))) do I
         Base.@_inline_meta