Lock solidus_core.gemspec to ransack '< 4.2'

Solidus core's gemspec already required that ransack be '~> 4.0', but
the latest version of ransack, v4.2.0, released July 10 2024, introduces
a bug. The previous implementation was taking for granted that every
predicate would respond to #value, which doesn't seem to be the case
when the predicate is an instance of a Arel::SelectManager.

This has already been flagged by @spaghetticode in his PR against
ransack: activerecord-hackery/ransack#1468

Since there has been little movement on this PR since January, we should
lock to a version that works for us since currently many of our product
specs are failing. (eg. spec/models/spree/product_spec.rb:659)

We can remove this lock once the PR is merged and once the above test
(and the others that are failing) are able to pass in ransack v4.2.0 or
subsequent versions.

core/solidus_core.gemspec

@@ -43,7 +43,9 @@ Gem::Specification.new do |s|
   s.add_dependency 'monetize', '~> 1.8'
   s.add_dependency 'kt-paperclip', ['>= 6.3', '< 8']
   s.add_dependency 'psych', ['>= 4.0.1', '< 6.0']
-  s.add_dependency 'ransack', '~> 4.0'
+  # @note ransack 4.2 contains a bug which has not yet been addressed.
+  # @see https://github.com/activerecord-hackery/ransack/pull/1468
+  s.add_dependency 'ransack', ['~> 4.0', '< 4.2']
   s.add_dependency 'sprockets-rails', '!= 3.5.0'
   s.add_dependency 'state_machines-activerecord', '~> 0.6'
   s.add_dependency 'omnes', '~> 0.2.2'