Use correct Fenix rebase branch

projects/fenix/config

 # vim: filetype=yaml sw=2
 version: '[% c("abbrev") %]'
 filename: 'fenix-[% c("version") %]-[% c("var/build_id") %].tar.gz'
-git_hash: 'tor-browser-[% c("var/fenix_version") %]-[% c("var/torbrowser_branch") %]-2-build1'
+git_hash: 'tor-browser-[% c("var/fenix_version") %]-[% c("var/torbrowser_branch") %]-1-build1'
 git_url: https://gitlab.torproject.org/tpo/applications/fenix.git
 tag_gpg_id: 1
 gpg_keyring: torbutton.gpg