remove installing synthtool

.github/workflows/verify_library_generation.yaml

@@ -88,21 +88,6 @@ jobs:
         pushd library_generation
         pip install -r requirements.txt
         popd
-    - name: install synthtool
-      shell: bash
-      run: |
-        set -ex
-        mkdir -p /tmp/synthtool
-        pushd /tmp/synthtool
-        if [ ! -d "synthtool" ]; then
-          git clone https://github.com/googleapis/synthtool.git
-        fi
-        pushd "synthtool"
-
-        git reset --hard origin/no-java-templates
-
-        python3 -m pip install -e .
-        python3 -m pip install -r requirements.in
     - name: Run shell unit tests
       run: |
         set -x