selinux: Permit read access to symbolic links in /var/lib/flatpak

Commit 8617ab0 granted read and lock access to
/var/lib/flatpak but didn't cover symbolic links.  This explicitly
permits that to avoid running into SELinux denials.

https://bugzilla.redhat.com/show_bug.cgi?id=2071215

selinux/flatpak.te

@@ -15,6 +15,7 @@ init_daemon_domain(flatpak_helper_t, flatpak_helper_exec_t)
 auth_read_passwd(flatpak_helper_t)
 files_list_var_lib(flatpak_helper_t)
 files_read_var_lib_files(flatpak_helper_t)
+files_read_var_lib_symlinks(flatpak_helper_t)
 
 ifdef(`corecmd_watch_bin_dirs',`
     corecmd_watch_bin_dirs(flatpak_helper_t)