Update issue_template.md

cosmetic change

Author: sm4rk0

.github/issue_template.md

@@ -1,6 +1,6 @@
 Thank you for your effort to improve this module!
 
-The xml module is upstream now and ships with Ansible v2.4 which is to be released in mid-September[1]
+The xml module is upstream now and ships with Ansible v2.4 which is to be released in mid-September:
 https://github.com/ansible/ansible/blob/devel/docs/docsite/rst/roadmap/ROADMAP_2_4.rst
 
 Please try running ansible from source: