Upgrade github actions to v4 (#213)

.github/workflows/ci.yml

@@ -50,7 +50,7 @@ jobs:
     continue-on-error: ${{ matrix.branch == 'devel' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install build dependencies (Linux i386)
         if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
@@ -103,7 +103,7 @@ jobs:
       - name: Restore Nim DLLs dependencies (Windows) from cache
         if: runner.os == 'Windows'
         id: windows-dlls-cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: external/dlls-${{ matrix.target.cpu }}
           key: 'dlls-${{ matrix.target.cpu }}'