count should be length

Example refers to a count function, which does not exist. Replacing it with length works.

docs/content/3.manual/manual.yml

@@ -946,7 +946,7 @@ sections:
           means that you'll sometimes have to be more explicit about
           the condition you want: you can't test whether, e.g. a
           string is empty using `if .name then A else B end`, you'll
-          need something more like `if (.name | count) > 0 then A else
+          need something more like `if (.name | length) > 0 then A else
           B end` instead.
           
           If the condition A produces multiple results, it is