CI: Update to actions/cache@v3

No functional changes for our use case, but we should keep this current.

.github/workflows/vtest.yml

@@ -58,7 +58,7 @@ jobs:
     - name: Cache SSL libs
       if: ${{ matrix.ssl && matrix.ssl != 'stock' && matrix.ssl != 'BORINGSSL=yes' && matrix.ssl != 'QUICTLS=yes' }}
       id: cache_ssl
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: '~/opt/'
         key: ssl-${{ steps.generate-cache-key.outputs.key }}
@@ -66,7 +66,7 @@ jobs:
     - name: Cache OpenTracing
       if: ${{ contains(matrix.FLAGS, 'USE_OT=1') }}
       id: cache_ot
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: '~/opt-ot/'
         key: ot-${{ matrix.CC }}-${{ env.OT_CPP_VERSION }}-${{ contains(matrix.name, 'ASAN') }}