ci: bump actions & fix syntax

Signed-off-by: Shengqi Chen <harry-chen@outlook.com>

Author: Harry-Chen

.github/workflows/test.yml

@@ -6,14 +6,14 @@ on:
 
 jobs:
     test:
-        runs-on: ubuntu-latest
-        if: "!contains(github.event.head_commit.message, 'ci skip')"
+        runs-on: ubuntu-24.04
+        if: ${{ !contains(github.event.head_commit.message, 'ci skip') }}
         strategy:
           matrix:
             sdk: [stable, beta]
 
         steps:
-          - uses: actions/checkout@v3
+          - uses: actions/checkout@v4
           - uses: dart-lang/setup-dart@v1
             with:
               sdk: ${{ matrix.sdk }}