Update PR template

.github/pull_request_template.md

@@ -1,5 +1,5 @@
 <!-- Please remember to select the appropriate branch:
 
-For bug or doc fixes pick the oldest branch where the bugfix applies (2.0 typically, or 1.10 if it is a critical fix that should be fixed in Composer 1) 
+For bug or doc fixes pick the oldest branch where the fix applies (e.g. 2.1 or similar if such a branch exists, or 1.10 if it is a critical fix that should be fixed in Composer 1)
 
 For new features and everything else, use the master branch. -->