ci: bump actions/cache from 4 to 5 (#25942)

Author: dependabot[bot]

.github/workflows/vpm_ci.yml

@@ -34,7 +34,7 @@ jobs:
         if: runner.os == 'Windows'
         run: cd vlang && ./make.bat && ./v doctor
       - name: Cache V
-        uses: actions/cache/save@v4
+        uses: actions/cache/save@v5
         with:
           path: vlang
           key: ${{ runner.os }}-${{ github.sha }}
@@ -62,7 +62,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Restore V cache
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@v5
         with:
           path: vlang
           key: ${{ runner.os }}-${{ github.sha }}