change build matrix

Author: lucascosti

.github/workflows/node_build.yml

@@ -13,7 +13,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest]
         node-version: [10.x, 12.x]
 
     name: Build using ${{ matrix.node-version }} on ${{ matrix.os }}