fix CI warn

Author: skudasov

.github/workflows/docs.yml

@@ -1,4 +1,4 @@
-name: GH Pages Deploy
+name: GH Pages Deploy (Docs, mdbook)
 
 
 on:
@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
 
       - name: Setup mdBook
         uses: peaceiris/actions-mdbook@v1