ci: license action use merge-base in git diff

Currently it takes git diff between main
and pull-request/merge commit. So if main moves
diff is incorrect and can cause false alarms.

Signed-off-by: Kari Hamalainen <kari.hamalainen@nordicsemi.no>

Author: karhama

.github/workflows/license-reusable.yml

@@ -93,7 +93,7 @@ jobs:
         ${ZEPHYR_BASE}/../nrf/scripts/ci/check_license.py \
             --github \
             -l ${ZEPHYR_BASE}/../${{ inputs.license_allow_list }} \
-            -c origin/${BASE_REF}..
+            -c origin/${BASE_REF}...
 
     - name: Upload results
       uses: actions/upload-artifact@4cec3d8aa04e39d1a68397de0c4cd6fb9dce8ec1 # v4