Actions: Remove duplicated gettext actions

[ryonakano]

Remove the duplicated gettext actions. merge.yml seems to be inactive after we migrated from master to main: https://github.com/elementary/icons/actions/workflows/merge.yml

ryonakano@fedora-host:~/work/elementary/icons (main =)$ diff -u --color .github/workflows/merge.yml .github/workflows/gettext.yml
--- .github/workflows/merge.yml	2026-09-21 16:27:25.224709892 +0900
+++ .github/workflows/gettext.yml	2026-09-21 16:25:05.093698751 +0900
@@ -1,11 +1,8 @@
----
-
-name: Merge
+name: Gettext Updates

 on:
   push:
-    branches:
-      - master
+    branches: [main]

 jobs:
   build:
@@ -18,6 +15,7 @@
       run: |
         apt-get update
         apt-get install git -y
+
     - name: Clone repository
       uses: actions/checkout@v7
       with:
ryonakano@fedora-host:~/work/elementary/icons (main =)$