updated workflow to eliminate unix shell syntax

.github/workflows/build.yml

@@ -18,7 +18,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install pyinstaller
-          if [ -f src/requirements.txt ]; then pip install -r src/requirements.txt; fi
+          pip install -r src/requirements.txt
       - name: Build Video2X CLI
         run: |
           pyinstaller --noconfirm --log-level=WARN \