Update appveyor.yml

Author: AtsushiSakai

appveyor.yml

@@ -38,7 +38,6 @@ install:
   - conda update -q conda
   - conda info -a
   - "python -m pip install --upgrade pip"
-  - "python -m pip install numpy"
   - conda env create -f C:\\projects\pythonrobotics\environment.yml
   - activate python_robotics