Update dependency installation in pofile.yml workflow

Let's use REQUIREMENTS.txt instead of listing incomplete dependencies

Author: DelazJ

.github/workflows/pofiles.yml

@@ -46,7 +46,7 @@ jobs:
     - name: Install dependencies
       run: |
           python -m pip install --upgrade pip
-          pip install sphinx sphinx-intl sphinxext.rediraffe pyYAML sphinx_togglebutton sphinx_copybutton
+          pip install -r REQUIREMENTS.txt
 
     - name: Generate English PO files
       id: "generate-po-files"