upgrade github actions to v3

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
     runs-on: ${{ matrix.builder }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install build dependencies (Linux i386)
         if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
@@ -91,7 +91,7 @@ jobs:
       - name: Restore Nim DLLs dependencies (Windows) from cache
         if: runner.os == 'Windows'
         id: windows-dlls-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: external/dlls
           key: 'dlls'