ci: update actions/cache to v4

Author: Wenzel

.github/workflows/ci.yml

@@ -304,7 +304,7 @@ jobs:
       - name: install cargo deb dependencies
         run: sudo apt-get install -y dpkg liblzma-dev
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry
@@ -403,7 +403,7 @@ jobs:
         id: get_version
         run: echo "version=${GITHUB_REF#refs/tags/}" >> $GITHUB_OUTPUT
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry
@@ -492,7 +492,7 @@ jobs:
     steps:
       - uses: actions/checkout@v1
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry