gs-app-details-page: Change the title to ‘Update Details’

It looks weird to show the package name and/or version in the dialog title. Instead, just consistently show ‘Update Details’.

If we later decide that we need to show the package name/version somewhere, the right place for it is lower down in the dialog, not in the title bar.

Signed-off-by: Philip Withnall pwithnall@endlessos.org

Fixes: #1460 (closed)

Closes #1460 (closed)