d/patches: Always present "Download" button before "Restart & Update"

"prepared-update" can get removed when refreshing package lists,
in which case an update attempt will fail. Re-requesting the download
is enough to recreate the update package, so presenting "download"
option to the user even if everything is already downloaded before
allowing them to actually trigger the update should workaround this
problem.

Closes #40
5 jobs for hack in 9 minutes and 43 seconds (queued for 1 second)
Status Job ID Name Coverage
  Package
passed #368030
librem5
package-pureos-byzantium

00:01:53

passed #368031
librem5:arm64
package-pureos-byzantium:arm64

00:06:34

 
  Test Package
passed #368032
librem5
autopkgtest-pureos-byzantium-package

00:01:15

passed #368034
librem5
check-tarball

00:01:22

passed #368033
librem5
lintian-pureos-byzantium-package

00:01:13