fix(ruby): disable Style/TrivialAccessors for spec_helper top-level method

The spec_helper.rb defines `def client; @client; end` at the top level
rather than using attr_reader, because attr_reader raises
  NoMethodError: undefined method 'attr_reader' for main:Object
in Ruby 3.2+ when called outside a class/module context.

Rubocop now flags the trivial def as Style/TrivialAccessors. Disable
the cop so both the runtime constraint and the linter are satisfied.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: josephschorr

spicedb-ruby/.rubocop.yml

@@ -60,3 +60,9 @@ Gemspec/DevelopmentDependencies:
 # rubygems MFA is for published gems; this is a path-only dev dependency.
 Gemspec/RequireMFA:
   Enabled: false
+
+# The top-level `def client; @client; end` in examples/spec_helper.rb cannot
+# use attr_reader because attr_reader is not available on main:Object in
+# Ruby 3.2+ outside a class/module context (raises NoMethodError at load time).
+Style/TrivialAccessors:
+  Enabled: false