Bump actions/setup-node from v1 to v2.1.5

Bumps [actions/setup-node](https://github.com/actions/setup-node) from v1 to v2.1.5.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@v1...46071b5)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/tests.yml

@@ -14,7 +14,7 @@ jobs:
       uses: actions/setup-ruby@v1
 
     - name: Set up Node
-      uses: actions/setup-node@v1
+      uses: actions/setup-node@v2.1.5
 
     - name: Restore bundler cache
       uses: actions/cache@v1