clean up workflow file

.github/workflows/build-book.yml

@@ -1,26 +1,14 @@
-# This is a basic workflow to help you get started with Actions
-
 name: build-book
 
-# Controls when the action will run. 
 on:
-  # Triggers the workflow on push or pull request events but only for the main branch
   push:
     branches: [ master ]
 
-  # Allows you to run this workflow manually from the Actions tab
-  workflow_dispatch:
-
-# A workflow run is made up of one or more jobs that can run sequentially or in parallel
 jobs:
-  # This workflow contains a single job called "build"
   build:
-    # The type of runner that the job will run on
     runs-on: ubuntu-latest
 
-    # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
-      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
 
       - name: Set up Python