update v3 to v4

Author: kailinzhuang

.github/workflows/dca_tests.yml

@@ -15,9 +15,9 @@ jobs:
         python-version: ["3.7", "3.8", "3.9"]
     steps:
       - name: Test DCA
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies