Fix Coverage upload on GHA

Author: adamchainz

.github/workflows/main.yml

@@ -47,6 +47,8 @@ jobs:
       with:
         name: coverage-data-${{ matrix.python-version }}
         path: '${{ github.workspace }}/.coverage.*'
+        include-hidden-files: true
+        if-no-files-found: true
 
   coverage:
     name: Coverage