Revert "Create dummy-ci.yml"

This reverts commit 674d79414e7b425ecd0957a5b06f402930a65f26.

.github/workflows/dummy-ci.yml

@@ -1,27 +0,0 @@
-name: Node CI (dummy)
-
-on:
-  push:
-    branches:
-      - support/for-dummy-action
-
-jobs:
-  build:
-
-    runs-on: ubuntu-latest
-
-    strategy:
-      matrix:
-        node-version: [10.x, 12.x]
-
-    steps:
-    - uses: actions/checkout@v1
-      
-    - name: Use Node.js ${{ matrix.node-version }}
-      uses: actions/setup-node@v1
-      with:
-        node-version: ${{ matrix.node-version }}
-        
-    - name: echo
-      run: |
-        echo node -v