CI: apt-get update before purging host packages

[chrislongros]

Motivation and Context

As reported in #18607, every qemu-x86 job currently fails at the Setup QEMU step with a 404 while fetching a Java package. The package-cleanup runs against a stale host's package index, so apt resolves a package version that has since been removed from the repository.

Description

• Run apt-get update before the package removal in qemu-1-setup.sh so the versions apt resolves match what the repository actually serves.

How Has This Been Tested?

Pushed to a fork branch; the full qemu matrix now passes the Setup QEMU step on every distro.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

Closes #18607

[behlendorf]

Thanks for sorting this out!