Unify expectations on spec components folder

In this PR (https://github.com/consul/consul/pull/4683) a new syntax was introduced
in the component specs to check that the component was not rendering.
It seems interesting to add this syntax to the rest of the cases and thus unify the way
we check that a component is not rendering.

spec/components/admin/budgets/duration_component_spec.rb

@@ -49,7 +49,7 @@ describe Admin::Budgets::DurationComponent do
 
       render Admin::Budgets::DurationComponent.new(durable).duration
 
-      expect(page.text).to be_empty
+      expect(page.native.inner_html).to be_empty
     end
 
     it "is not defined when no start date is defined" do
@@ -57,7 +57,7 @@ describe Admin::Budgets::DurationComponent do
 
       render Admin::Budgets::DurationComponent.new(durable).duration
 
-      expect(page.text).to be_empty
+      expect(page.native.inner_html).to be_empty
     end
   end
 

spec/components/admin/budgets_wizard/headings/group_switcher_component_spec.rb

@@ -6,8 +6,7 @@ describe Admin::BudgetsWizard::Headings::GroupSwitcherComponent do
 
     render_inline Admin::BudgetsWizard::Headings::GroupSwitcherComponent.new(group)
 
-    expect(page.text).to be_empty
-    expect(page).not_to have_css ".budget-group-switcher"
+    expect(page.native.inner_html).to be_empty
   end
 
   it "renders a link to switch group for budgets with two groups" do