ci(openwrt): bump Node 20 actions to Node 24 majors

checkout v4->v6, cache v4->v5, upload-artifact v4->v7,
download-artifact v4->v8 to clear the Node 20 runner deprecation.

.github/workflows/package-openwrt.yml

@@ -26,7 +26,7 @@ jobs:
       package_version: ${{ steps.version.outputs.package_version }}
       release_channel: ${{ steps.channel.outputs.release_channel }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -96,7 +96,7 @@ jobs:
             # x86 routers / VMs
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -124,7 +124,7 @@ jobs:
 
       - name: Cache Cargo registry + build
         if: ${{ env.ACT != 'true' }}
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: |
             ~/.cargo/registry
@@ -395,7 +395,7 @@ jobs:
 
       - name: Upload artifact (GitHub only)
         if: ${{ env.ACT != 'true' }}
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: ${{ env.PACKAGE_FILENAME }}
           path: dist/${{ env.PACKAGE_FILENAME }}
@@ -519,7 +519,7 @@ jobs:
 
     steps:
       - name: Download all .ipk artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           path: dist
           merge-multiple: true