use different ubuntu version

.github/workflows/python-package-conda.yml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   build-linux:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     strategy:
       max-parallel: 5
 
@@ -29,10 +29,10 @@ jobs:
       run: |
         conda update conda -y -q
         conda config --add channels conda-forge
-        pip install scikit-learn==1.1.2
-        pip install pandas==1.3.5
-        pip install tensorflow joblib pytest
-        pip install imageio scikit-image
+        conda update conda -y -q
+        conda install scikit-learn=1.0.2 pandas=1.3.5  -y -q
+        conda install tensorflow joblib pytest -y -q
+        conda install imageio scikit-image -y -q
         conda install dlib -y -q
         pip install markdown
         pip install coverage