Bump checkout to v4

Author: warmwaffles

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
         elixir: ["1.17"]
         otp: ["27"]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         with:
           otp-version: ${{ matrix.otp }}
@@ -49,7 +49,7 @@ jobs:
           - elixir: "1.17"
             otp: "24"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         with:
           otp-version: ${{ matrix.otp }}