Fix HAML to comply Style/RedundantParentheses

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

ee/app/views/layouts/header/_read_only_banner.html.haml

@@ -2,6 +2,6 @@
 - if message
   .flash-container.flash-container-page
     .flash-notice.flash-notice-persistent
-      %div{ class: (container_class) }
+      %div{ class: container_class }
         %span
           = message

ee/app/views/shared/billings/_billing_plan.html.haml

@@ -70,6 +70,6 @@
       - show_contact_sales_button = show_contact_sales_button?(purchase_link.action, plan_offer_type)
       .gl-min-h-7.gl-display-flex.gl-flex-wrap.gl-justify-content-end
         - if show_contact_sales_button
-          = link_to s_('BillingPlan|Contact sales'), "#{contact_sales_url}?test=inappcontactsales#{plan.code}", class: [("btn gl-button"), (show_upgrade_button ? "btn-success-secondary" : "btn-success")], data: { **experiment_tracking_data_for_button_click('contact_sales') }
+          = link_to s_('BillingPlan|Contact sales'), "#{contact_sales_url}?test=inappcontactsales#{plan.code}", class: ["btn gl-button", show_upgrade_button ? "btn-success-secondary" : "btn-success"], data: { **experiment_tracking_data_for_button_click('contact_sales') }
         - if show_upgrade_button
           = link_to upgrade_button_text, plan_purchase_or_upgrade_url(namespace, plan), class: "#{upgrade_button_classes} billing-cta-purchase#{cta_class} gl-ml-3", data: { **experiment_tracking_data_for_button_click('upgrade') }