docs: update pr template to say default branch

Author: jsjoeio

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

@@ -2,7 +2,7 @@
 Please link to the issue this PR solves.
 If there is no existing issue, please first create one unless the fix is minor.
 
-Please make sure the base of your PR is the master branch!
+Please make sure the base of your PR is the default branch!
 -->
 
 ## Checklist