fix: partial CI fix and fix compiler error for "make tests"
CI is broken right now. Not all jobs can succeed due to used rust version of base image redoxos/redoxer.
Job linux for CI at least does not fail to rust version.
Other jobs "link-check", "linux:stable" and "redox" still fail. This relates to the issue #1020 (closed).
Command "make tests" executes without an error to due used rust version. This relates to the issue #1018 (closed) .