Rename count to index for clarity

src/hello/print/print_display/testcase_list.md

diff --git a/src/hello/print/print_display/testcase_list.md b/src/hello/print/print_display/testcase_list.md
index d07316b..c72c197 100644
--- a/src/hello/print/print_display/testcase_list.md
+++ b/src/hello/print/print_display/testcase_list.md
@@ -31,11 +31,11 @@
         write!(f, "[")?;
 
         // Iterate over `v` in `vec` while enumerating the iteration
-        // count in `count`.
-        for (count, v) in vec.iter().enumerate() {
+        // index in `index`.
+        for (index, v) in vec.iter().enumerate() {
             // For every element except the first, add a comma.
             // Use the ? operator to return on errors.
-            if count != 0 { write!(f, ", ")?; }
+            if index != 0 { write!(f, ", ")?; }
             write!(f, "{}", v)?;
         }