Upgrade github action to v3 (#150)

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
     continue-on-error: ${{ matrix.branch == 'version-1-6' || matrix.branch == 'devel' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           submodules: true
 
@@ -102,7 +102,7 @@ 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-${{ matrix.target.cpu }}
           key: 'dlls-${{ matrix.target.cpu }}'
@@ -183,7 +183,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           submodules: true