[NFC] polish .github/workflows/build.yml code style (#1837)

.github/workflows/build.yml

@@ -1,6 +1,6 @@
 name: Build
 
-on: 
+on:
   pull_request:
     types: [synchronize, labeled]
 
@@ -32,7 +32,7 @@ jobs:
       - uses: actions/checkout@v2
         with:
           ssh-key: ${{ secrets.SSH_KEY_FOR_CI }}
-      - name: Install Colossal-AI      
+      - name: Install Colossal-AI
         run: |
           [ ! -z "$(ls -A /github/home/cuda_ext_cache/)" ] && cp -r /github/home/cuda_ext_cache/* /__w/ColossalAI/ColossalAI/
           pip install -r requirements/requirements.txt