Update changelog

Let's have this in 0.0.20 so the `Breaks:` in librem5-base-defaults
stays correct.
4 jobs for pureos/byzantium in 2 minutes and 13 seconds (queued for 1 second)
Status Job ID Name Coverage
  Package
passed #363625
librem5
package-pureos-byzantium

00:00:38

passed #363626
librem5:arm64
package-pureos-byzantium:arm64

00:02:12

 
  Test Package
passed #363627
librem5
autopkgtest-pureos-byzantium-package

00:00:48

passed #363628
librem5
lintian-pureos-byzantium-package

00:00:42