actions: fix CI badge and run apt update

Author: lonvia

.github/actions/ubuntu-prerequisites/action.yml

@@ -6,6 +6,7 @@ runs:
   steps:
     - name: Remove preinstalled postgresql
       run: |
+        sudo apt update -qq
         sudo apt-get remove -yq postgresql*
       shell: bash
 

README.md

@@ -7,7 +7,7 @@ database suitable for applications like rendering into a map, geocoding with
 Nominatim, or general analysis.
 
 [![Appveyor Build Status](https://ci.appveyor.com/api/projects/status/7abwls7hfmb83axj/branch/master?svg=true)](https://ci.appveyor.com/project/openstreetmap/osm2pgsql/branch/master)
-[![Github Actions Build Status](https://github.com/openstreetmap/osm2pgsql/workflows/OSX%20CI/badge.svg?branch=master)](https://github.com/openstreetmap/osm2pgsql/actions)
+[![Github Actions Build Status](https://github.com/openstreetmap/osm2pgsql/workflows/CI/badge.svg?branch=master)](https://github.com/openstreetmap/osm2pgsql/actions)
 [![Packaging Status](https://repology.org/badge/tiny-repos/osm2pgsql.svg)](https://repology.org/project/osm2pgsql/versions)
 
 ## Features ##