fix: Auto resolution flaky spec (#11964)

The test was failing because Current.contact was not being cleared when
testing system auto-resolution. Added Current.contact = nil to ensure
the system auto-resolution message is triggered instead of contact
resolution.

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---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

spec/models/conversation_spec.rb

@@ -215,7 +215,7 @@ RSpec.describe Conversation do
     it 'adds a message for system auto resolution if marked resolved by system' do
       account.update(auto_resolve_after: 40 * 24 * 60)
       conversation2 = create(:conversation, status: 'open', account: account, assignee: old_assignee)
-      Current.user = nil
+      Current.reset
 
       message_data = if account.auto_resolve_after >= 1440 && account.auto_resolve_after % 1440 == 0
                        { key: 'auto_resolved_days', count: account.auto_resolve_after / 1440 }