[release-11.3.5] CI: remove unnecessary line in backport.yml (#102609)

CI: remove unnecessary line in backport.yml (#100144)

remove bad line

(cherry picked from commit 8e10ee9056)

Co-authored-by: Kevin Minehart <5140827+kminehart@users.noreply.github.com>

.github/workflows/backport.yml

@@ -12,7 +12,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-          ref: main
       - name: "Generate token"
         id: generate_token
         uses: tibdex/github-app-token@b62528385c34dbc9f38e5f4225ac829252d1ea92