update python version in building linux wheel

Author: Jinyu Wang

.github/workflows/build_wheel.yml

@@ -45,7 +45,7 @@ jobs:
       if: runner.os == 'Linux' && matrix.python-version == '3.7'
       uses: RalfG/python-wheels-manylinux-build@v0.3.1-manylinux2010_x86_64
       with:
-        python-versions: 'cp36-cp36m cp37-cp37m'
+        python-versions: 'cp37-cp37m cp38-cp38m cp39-cp39m'
         build-requirements: 'numpy'
         pip-wheel-args: '-w ./wheelhouse' # save wheel packages to wheelhouse folder
         pre-build-command: 'export LD_LIBRARY_PATH=/usr/local/lib/:$LD_LIBRARY_PATH'