Comment out template (#1520)

.github/ISSUE_TEMPLATE/bug_report.md

@@ -10,7 +10,7 @@ assignees: ''
 ---
 
 **Describe the bug**
-A clear and concise description of what the bug is, steps to reproduce, expected behavior, etc.
+<!-- A clear and concise description of what the bug is, steps to reproduce, expected behavior, etc. -->
 
 **Additional context**
-Add any other context about the problem here (e.g. OS, Arbor version, etc.).
+<!-- Add any other context about the problem here (e.g. OS, Arbor version, etc.). -->

.github/pull_request_template.md

-Please make sure your PR follows our [contribution guidelines](https://github.com/arbor-sim/arbor/tree/master/doc/contrib) and agree to the terms outlined in the [PR procedure](https://github.com/arbor-sim/arbor/tree/master/doc/contrib/pr.rst).
+<!-- Please make sure your PR follows our [contribution guidelines](https://github.com/arbor-sim/arbor/tree/master/doc/contrib) and agree to the terms outlined in the [PR procedure](https://github.com/arbor-sim/arbor/tree/master/doc/contrib/pr.rst). -->