Try a different syntax for github actions excludes

Refs: actions/runner#1512

Author: kvakil

.github/workflows/push.yml

@@ -32,12 +32,8 @@ jobs:
         os: [ubuntu-18.04, ubuntu-20.04]
         llvm: [8, 9, 10, 11, 12, 13, 14]
         exclude:
-          - os: ubuntu-18.04
-            node:
-              - version: 18.x
-          - os: ubuntu-18.04
-            node:
-              - version: 19.x
+          - {os: ubuntu-18.04, node: {version: 18.x}}
+          - {os: ubuntu-18.04, node: {version: 19.x}}
     steps:
       - uses: actions/checkout@v1
       - name: Use Node.js ${{ matrix.node.version }} ${{ matrix.node.mirror }}