Small clean up in client spec (#2778)

* chore(specs): minor formatting fix

* fix(specs): remove global class from client spec

Author: solnic

sentry-ruby/spec/sentry/client_spec.rb

@@ -1,21 +1,14 @@
 # frozen_string_literal: true
 
-class ExceptionWithContext < StandardError
-  def sentry_context
-    {
-      foo: "bar"
-    }
-  end
-end
-
 RSpec.describe Sentry::Client do
+  subject { Sentry::Client.new(configuration) }
+
   let(:configuration) do
     Sentry::Configuration.new.tap do |config|
       config.dsn = Sentry::TestHelper::DUMMY_DSN
       config.transport.transport_class = Sentry::DummyTransport
     end
   end
-  subject { Sentry::Client.new(configuration) }
 
   let(:hub) do
     Sentry::Hub.new(subject, Sentry::Scope.new)
@@ -571,8 +564,18 @@ module ExcTag; end
       end
 
       context 'when the exception responds to sentry_context' do
+        let(:exception_with_context) do
+          Class.new(StandardError) do
+            def sentry_context
+              {
+                foo: "bar"
+              }
+            end
+          end
+        end
+
         let(:hash) do
-          event = subject.event_from_exception(ExceptionWithContext.new)
+          event = subject.event_from_exception(exception_with_context.new)
           event.to_h
         end