docks: add missing colon character

Without the missing colon character, the code block that followed
wasn't rendering properly.

Signed-off-by: Micah Abbott <miabbott@redhat.com>

docs/docsite/rst/playbooks_loops.rst

@@ -520,7 +520,7 @@ Subsequent loops over the registered variable to inspect the results may look li
       when: item.rc != 0
       with_items: "{{ echo.results }}"
 
-During iteration, the result of the current item will be placed in the variable:
+During iteration, the result of the current item will be placed in the variable::
 
     - shell: echo "{{ item }}"
       with_items: