Try to use pip instead of conda to build pytraj

.github/workflows/merge-gate.yml

@@ -142,13 +142,10 @@ jobs:
       uses: actions/setup-python@v4
       with:
         python-version: 3.8
-    - name: Add conda to system path
+    - name: Install dependencies
       run: |
-        # $CONDA is an environment variable pointing to the root of the miniconda directory
-        echo $CONDA/bin >> $GITHUB_PATH
-    - name: Install conda packages
-      run: |
-        conda install setuptools cython numpy pytest mock curl 
+        python -m pip install --upgrade pip
+        pip install setuptools cython numpy pytest mock curl
     - name: Install cpptraj
       run: |
         export PATH=$HOME/bin:${PATH}