Bug 40916: Pull Mullvad mar files from archive.torproject.org

In order to generate incrementals, get mar files from the previous
version from archive.tpo instead of the Mullvad mirrors, since that
release is not always there but should always be on archive.tpo.

projects/release/update_responses_config.yml

@@ -10,13 +10,12 @@ appname_bundle_win64: '[% c("var/projectname") %]-install-win64'
 releases_dir: [% path(c('output_dir')) %][% IF ! c("var/nightly") %]/signed[% END %]
 download:
     gpg_keyring: ../../keyring/torbrowser.gpg
+    archive_url: 'https://archive.torproject.org/tor-package-archive/[% c("var/projectname") %]'
 [% IF c("var/tor-browser") -%]
-    archive_url: 'https://archive.torproject.org/tor-package-archive/torbrowser'
     bundles_url: 'https://dist.torproject.org/torbrowser'
     mars_url: 'https://cdn.torproject.org/aus1/torbrowser'
 [% END -%]
 [% IF c("var/mullvad-browser") -%]
-    archive_url: 'https://cdn.mullvad.net/browser'
     bundles_url: 'https://cdn.mullvad.net/browser'
     mars_url: 'https://cdn.mullvad.net/browser'
 [% END -%]