add pip install update

Author: antgonza

.github/workflows/qiita-plugin-ci.yml

@@ -64,6 +64,7 @@ jobs:
           conda config --add channels conda-forge
           conda create -q --yes -n qiita python=3.6 pip==9.0.3 libgfortran numpy nginx cython redis
           conda activate qiita
+          pip install --upgrade pip
           pip install sphinx sphinx-bootstrap-theme nose-timer codecov Click
 
       - name: Qiita install