Fix a typo in stack's docs

src/primitive/defs.rs

@@ -3145,7 +3145,7 @@ primitive!(
     ///   : ++
     /// Subscripted [stack] prints that many values from the stack.
     /// ex: ?₂ 1 2 3 4
-    /// If you type `N+1`` `?`s, it will format to [stack] subscripted with `N`.
+    /// If you type `N+1` `?`s, it will format to [stack] subscripted with `N`.
     /// ex: ??? 1 2 3 4 # Try formatting!
     (0(0), Stack, Debug, ("stack", '?'), Impure),
     /// Debug print the top value on the stack without popping it