Update build-sphinx.yml (#88)

* Update build-sphinx.yml

adds an update apt-get in the build configuration file.

Author: wsavran

.github/workflows/build-sphinx.yml

@@ -17,6 +17,7 @@ jobs:
           python-version: 3.7
       - name: Install dependencies
         run: |
+          sudo apt-get update
           sudo apt-get install libproj-dev proj-data proj-bin
           sudo apt-get install libgeos-dev
           sudo apt-get install python3-sphinx