Bump GitHub action versions in reusable_testing.yml

- actions/checkout: v2 -> v3
- actions/download-artifact: v2 -> v3

NO_DOC=ci
NO_TEST=ci

Author: ylobankov

.github/workflows/reusable_testing.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: 'Clone the vshard module'
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           repository: ${{ github.repository_owner }}/vshard
           # Fetch the entire history for all branches and tags. It is needed for
@@ -25,7 +25,7 @@ jobs:
           submodules: recursive
 
       - name: 'Download the tarantool build artifact'
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v3
         with:
           name: ${{ inputs.artifact_name }}