Revert "Manually add wheezy security repo key"

This reverts commit 2c02d14f.

Debian fixed its security repo signing key.

Closes Librem5/image-builder#17

root.sh

@@ -207,8 +207,6 @@ EOF
 
     chroot ${basedir} apt-get install -y gnupg
     cat data/ci-repo.key | chroot ${basedir} apt-key add -
-    # Temporarily needed for the security repo to work. See https://source.puri.sm/Librem5/image-builder/merge_requests/46
-    cat data/wheezy-security.key | chroot ${basedir} apt-key add -
 }