Revert "Prep for next release 8.16 (#3914)"

This reverts commit ac8f730.

Author: eric-forte-elastic

.github/workflows/lock-versions.yml

@@ -6,7 +6,7 @@ on:
           description: 'List of branches to lock versions (ordered, comma separated)'
           required: true
           # 7.17 was intentionally skipped because it was added late and was bug fix only
-          default: '8.10,8.11,8.12,8.13,8.14,8.15'
+          default: '8.9,8.10,8.11,8.12,8.13,8.14'
 
 jobs:
   pr: