Revert "chore: add v15 to POT file mix" (#25990)

* Revert "chore: add v15 to POT file mix (#25983)"

This reverts commit c94de176c9.

* Update generate-pot-file.yml

.github/workflows/generate-pot-file.yml

@@ -1,6 +1,3 @@
-# This workflow is agnostic to branches. Only maintain on develop branch.
-# To add/remove branches just modify the matrix.
-
 name: Regenerate POT file (translatable strings)
 on:
   schedule:
@@ -15,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        branch: ["develop", "version-15-hotfix"]
+        branch: ["develop"]
     permissions:
       contents: write