Fix(LLMLingua): fix unitest

.github/workflows/unittest.yml

@@ -32,7 +32,7 @@ jobs:
       - name: Install packages and dependencies for all tests
         run: |
           python -m pip install --upgrade pip wheel
-          pip install pytest pytest-xdist
+          pip install pytest pytest-xdist nltk
           python -c "import nltk; nltk.download('punkt_tab')"
 
       - name: Install packages