docs(pr): remove PR template to use org-wide template instead [skip ci]

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,8 +0,0 @@
-**Summary of Changes**
- * Issue summary 
- - Indented line 1
- - Indented line 2
-**Testing**
- - Ran `make`
- - Tested in Vagrant
- - Tested on OS