If you choose 'Yes' here it will update all 'focal' to 'jammy' entries -- but it doesn't

[strk]

This is my starting /etc/apt/source.list:
```
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu focal main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu focal-updates main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu focal-backports main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu focal-security main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/pgdg/pub/repos/apt focal-pgdg main
deb [trusted=yes arch=amd64] http://apt.cust.om/cust-ubuntu/ focal-backports main
```

When running do-release-upgrade it tells me:

  No valid mirror found
  Do you want to rewrite your 'sources.list' file anyway?
  If you choose 'Yes' here it will update all 'focal' to 'jammy' entries.

I chose 'Yes' and this is the resulting /etc/apt/source.list:
```
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu jammy main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu jammy-updates main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu jammy-backports main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/ubuntu jammy-security main restricted universe multiverse
deb [trusted=yes arch=amd64] http://apt.cust.om/pgdg/pub/repos/apt focal-pgdg main
# deb [trusted=yes arch=amd64] http://apt.cust.om/cust-ubuntu/ focal-backports main
```

As you can see the second-last line did not get "focal" replaced by "jammy".

Also I don't know why the last line was disabled.