Revert "ci: bump node version to see if this fixes the break"

This reverts commit b300026.

Author: JohannesHoppe

.github/workflows/main.yml

@@ -10,10 +10,10 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
 
-      - name: Use Node.js 12.x
+      - name: Use Node.js 10.x
         uses: actions/setup-node@v1
         with:
-          node-version: 12.x
+          node-version: 10.x
 
       - name: Prepare
         run: |