workflows: reuse DCO from org-wide repo

One line instead of many lines here.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

.github/workflows/dco.yml

@@ -6,16 +6,5 @@ on:
       - master
 
 jobs:
-  commits_check_job:
-    runs-on: ubuntu-latest
-    name: Commits Check
-    steps:
-    - name: Get PR Commits
-      id: 'get-pr-commits'
-      uses: tim-actions/get-pr-commits@master
-      with:
-        token: ${{ secrets.GITHUB_TOKEN }}
-    - name: DCO Check
-      uses: tim-actions/dco@master
-      with:
-        commits: ${{ steps.get-pr-commits.outputs.commits }}
+  dco:
+    uses: nspcc-dev/.github/.github/workflows/dco.yml@master