Update DeltaTest workflow to install dependencies from docs/requirements.txt

.github/workflows/deltatest.yaml

@@ -30,7 +30,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+          pip install -r docs/requirements.txt
           pip install deltatest-cli
 
       - name: Run Affected Tests
@@ -39,4 +39,3 @@ jobs:
           DELTA_REPO_ID: 39ee0ac5-e440-4cc9-9300-4868186133a8
         run: |
           delta run
-