Update github cache action

Author: tfwright

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
         with:
           elixir-version: ${{ matrix.elixir }}
           otp-version: ${{ matrix.otp }}
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: deps
           key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-deps-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
@@ -50,7 +50,7 @@ jobs:
         with:
           elixir-version: ${{ matrix.elixir }}
           otp-version: ${{ matrix.otp }}
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: _build
           key: build-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
@@ -61,7 +61,7 @@ jobs:
           mix deps.get
       - name: Create plts dir
         run: mkdir -p priv/plts
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: priv/plts
           key: plts-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}