Update checkouts

.github/workflows/ci.yaml

           - ^1.25
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           submodules: recursive
 
     timeout-minutes: 20
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           submodules: recursive
 
     timeout-minutes: 5
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           submodules: recursive
 
     timeout-minutes: 20
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           submodules: recursive