Declare logger as a runtime dependency

[tas50]

Description

lib/license_acceptance/config.rb requires logger, and Config#initialize calls ::Logger.new(IO::NULL) on the default path:

@logger = opts.fetch(:logger, ::Logger.new(IO::NULL))

So logger is a runtime dependency in practice. It was never declared, which was harmless while logger was a default gem.

Ruby 4.0 moved logger from a default gem to a bundled gem:

Gem::BUNDLED_GEMS::SINCE["logger"]                                 # => "4.0.0"
Gem::Specification.find_all_by_name("logger").first.default_gem?   # => false

Bundled gems ship with Ruby but are not on the load path of a bundle that doesn't ask for them. Under Ruby 4.0 the gem therefore fails to load at all:

	result
before	LoadError: cannot load such file -- logger — 0 examples, 1 error outside of examples
after	124 examples, 0 failures

Scope

logger is the only require in lib/ this affects. I cross-referenced every stdlib require in the gem against Gem::BUNDLED_GEMS::SINCE:

require	status on Ruby 4.0
logger	bundled since 4.0.0 — must be declared
date, timeout, forwardable, fileutils, etc, yaml	still default gems, stay undeclared

Constraint

Declared without a version constraint, matching how ruby/syslog and ruby/rbs handled the same transition. The logger gem supports well below this gemspec's required_ruby_version = ">= 2.5", so no floor is needed and older rubies keep resolving the version they already had.

Note on CI

This is not the current red CI, which is Security/YAMLLoad under Cookstyle 9.0.0 — fixed separately in #134. This PR is branched off main, so it will show those same 4 pre-existing lint offenses until #134 lands.

It does, however, break any consumer bundling this gem on Ruby 4.0 — including inspec-core and kitchen-omnibus-chef, both of which depend on license-acceptance.