Bump GitHub action versions in reusable_testing.yml

- actions/download-artifact: v2 -> v3

Author: Islam Elkanov

.github/workflows/reusable_testing.yml

@@ -27,7 +27,7 @@ jobs:
           submodules: recursive
 
       - name: Download the tarantool build artifact
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v3
         with:
           name: ${{ inputs.artifact_name }}