data-sync-maintainers: checkout the dispatched ref, not hardcoded main

The checkout step pinned `ref: main`, so a manual workflow_dispatch from a branch
still ran main's files (generate_CODEOWNERS.sh, board configs) — making it
impossible to test a change to those from a branch: the inactive maintainers got
flagged (that logic is in the workflow yaml, which DOES come from the branch) but
CODEOWNERS was regenerated by main's unfiltered script, so the auto-PR showed no
change.

Use `ref: ${{ github.ref_name }}`: the scheduled run (on main) is unchanged, while
a manual run from a branch checks out that branch and exercises its code.

Signed-off-by: Igor Pecovnik <igor@armbian.com>

Author: igorpecovnik

.github/workflows/data-sync-maintainers.yml

@@ -25,7 +25,12 @@ jobs:
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           repository: armbian/build
-          ref:  main
+          # Follow the dispatched ref: the scheduled run is on main (so this is
+          # 'main' there), but a manual workflow_dispatch from a branch checks out
+          # THAT branch — so changes to generate_CODEOWNERS.sh / configs can be
+          # tested end-to-end before merge (was hardcoded 'main', which always ran
+          # main's files regardless of where you dispatched from).
+          ref: ${{ github.ref_name }}
           fetch-depth: 0
           clean: false