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/shared/link_list_component_spec.rb

@@ -4,13 +4,13 @@ describe Shared::LinkListComponent do
   it "renders nothing with an empty list" do
     render_inline Shared::LinkListComponent.new
 
-    expect(page).not_to have_css "ul"
+    expect(page.native.inner_html).to be_empty
   end
 
   it "returns nothing with a list of nil elements" do
     render_inline Shared::LinkListComponent.new(nil, nil)
 
-    expect(page).not_to have_css "ul"
+    expect(page.native.inner_html).to be_empty
   end
 
   it "generates a list of links" do