fix: ci: Remove reuse annotations for unused m4 libtool files

The files in question are no longer included in the git tree and
distributed with the code. Remove the reuse annotations as they caused
issues with reuse 6.0.0, as multiline annotation for
SPDX-FileCopyrightText breaks the parsing.

Merge branch 'nicki/reuse-remove-m4-annotations' into 'main'

See merge request isc-projects/bind9!11056