fixed missing dependency for gh action

.github/workflows/preflight_validation.yaml

@@ -24,14 +24,11 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install flake8 pytest pytest-cov defusedxml black
+        pip install flake8 pytest pytest-cov defusedxml
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Lint with flake8
       run: |
         flake8 --exclude test,docs,examples .
-    - name: Check Syntax with PSF/Black
-      run: |
-        black -l 79 --check . --exclude="tests/|venv|.tox"
     - name: Test with pytest
       run: |
         pytest --cov=libnmap/ --ignore=libnmap/test/test_backend_plugin_factory.py