Rename helper method for clarity

Renames a helper method in EE::NamespaceStorageLimitAlertHelper from
`can_purchase_storage_for_namespace?` to
`purchase_storage_link_enabled?` for clarity. The previous name gave
the impression this involved user abilities which is does not.

Also removes a method, `can_purchase_storage?`, that is no longer used.

ee/app/helpers/ee/namespace_storage_limit_alert_helper.rb

@@ -46,7 +46,7 @@ module EE
       end
     end
 
-    def can_purchase_storage_for_namespace?(namespace)
+    def purchase_storage_link_enabled?(namespace)
       ::Feature.enabled?(:buy_storage_link) &&
         namespace.additional_repo_storage_by_namespace_enabled?
     end
@@ -59,11 +59,6 @@ module EE
       end
     end
 
-    def can_purchase_storage?
-      ::Gitlab::CurrentSettings.enforce_namespace_storage_limit? &&
-        ::Feature.enabled?(:buy_storage_link)
-    end
-
     def purchase_storage_url
       EE::SUBSCRIPTIONS_MORE_STORAGE_URL
     end

ee/app/views/groups/usage_quotas/index.html.haml

 - page_title s_("UsageQuota|Usage")
-- url_to_purchase_storage = purchase_storage_url if can_purchase_storage_for_namespace?(@group)
+- url_to_purchase_storage = purchase_storage_url if purchase_storage_link_enabled?(@group)
 
 %h3.page-title
   = s_('UsageQuota|Usage Quotas')
@@ -22,4 +22,3 @@
       locals: { namespace: @group, projects: @projects }
   .tab-pane#storage-quota-tab
     #js-storage-counter-app{ data: { namespace_path: @group.full_path, help_page_path: help_page_path('user/group/index.md', anchor: 'storage-usage-quota'), purchase_storage_url: url_to_purchase_storage, is_temporary_storage_increase_visible: temporary_storage_increase_visible?(@group).to_s } }
-

ee/app/views/profiles/usage_quotas/index.html.haml

 - page_title s_("UsageQuota|Usage")
 - @content_class = "limit-container-width" unless fluid_layout
-- url_to_purchase_storage = purchase_storage_url if can_purchase_storage_for_namespace?(@namespace)
+- url_to_purchase_storage = purchase_storage_url if purchase_storage_link_enabled?(@namespace)
 
 %h3.page-title
   = s_('UsageQuota|Usage Quotas')

ee/app/views/shared/_namespace_storage_limit_alert.html.haml

@@ -11,7 +11,7 @@
 
 - style = namespace_storage_alert_style(alert_level)
 - icon = namespace_storage_alert_icon(alert_level)
-- purchase_link = purchase_storage_url if can_purchase_storage_for_namespace?(namespace)
+- purchase_link = purchase_storage_url if purchase_storage_link_enabled?(namespace)
 - usage_link = namespace_storage_usage_link(root_namespace)
 - show_storage_banner_actions = purchase_link || usage_link
 

ee/spec/helpers/ee/namespace_storage_limit_alert_helper_spec.rb

@@ -72,26 +72,6 @@ RSpec.describe EE::NamespaceStorageLimitAlertHelper do
     end
   end
 
-  describe '#can_purchase_storage?' do
-    subject { helper.can_purchase_storage? }
-
-    where(:enforcement_setting_enabled, :feature_enabled, :result) do
-      false | false | false
-      false | true  | false
-      true  | false | false
-      true  | true  | true
-    end
-
-    with_them do
-      before do
-        stub_application_setting(enforce_namespace_storage_limit: enforcement_setting_enabled)
-        stub_feature_flags(buy_storage_link: feature_enabled)
-      end
-
-      it { is_expected.to eq(result) }
-    end
-  end
-
   describe '#purchase_storage_url' do
     subject { helper.purchase_storage_url }
 
@@ -196,8 +176,8 @@ RSpec.describe EE::NamespaceStorageLimitAlertHelper do
     end
   end
 
-  describe '#can_purchase_storage_for_namespace?' do
-    subject { helper.can_purchase_storage_for_namespace?(namespace) }
+  describe '#purchase_storage_link_enabled?' do
+    subject { helper.purchase_storage_link_enabled?(namespace) }
 
     let_it_be(:namespace) { build(:namespace) }