CTR update PR template

Author: xiazcy

.github/pull_request_template.md

@@ -1,8 +1,8 @@
 <!--
 Thanks for contributing! Reminders:
 + TARGET the earliest branch where you want the change
-    3.7-dev -> 3.7.6 (non-breaking only)
-    3.8-dev -> 3.8.1 (non-breaking only)
+    3.7-dev -> 3.7.7 (non-breaking only)
+    3.8-dev -> 3.8.2 (non-breaking only)
     master  -> 4.0.0
 + Committers will MERGE the PR forward to newer versions
 + ADD entry to the CHANGELOG.asciidoc for the targeted version