Comment the PR template

People keep sending PRs with the text intact, comment it out for my sanity :)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,8 @@
+<!--
 Thanks for the Pull Request!  We really appreciate your help and contribution!
 
 Before you submit the PR, have you signed Contributor License Agreement: https://www.elastic.co/contributor-agreement/ ?
 
 PR's (no matter how small) cannot be merged until the CLA has been signed.  
 It only needs to be signed once, however. Thanks!
+-->