ci: fix workflow typo (#24)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ad4ecc0..37b47f8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -31,7 +31,7 @@
 
     steps:
       - uses: actions/checkout@v2
-        uses: actions/setup-node@v2
+      - uses: actions/setup-node@v2
         with:
           node-version: ${{ matrix.node-version }}