Use Capybara methods to find/click/check links

We applied the Capybara/SpecificMatcher in commit f52a86b46.  However,
this rule doesn't convert methods finding <a> tags to methods finding
links because <a> tags only count as links when they've got the `href`
attribute. For instance, in the `xss_spec.rb` file we check what happens
when clicking on an anchor tag because we're testing that the `href`
attribute has been removed and so we can't use `click_link`.

So, basically, we can't enable a rule to automatically detect when we're
using `have_css` instead of `have_link`, but we should still do it
because `have_link` adds an extra check which affects accessibility
since it makes sure the tag has the `href` attribute and so it's
recognizable as a link by screen readers.

spec/components/budgets/phases_component_spec.rb

@@ -11,7 +11,6 @@ describe Budgets::PhasesComponent do
     budget.current_phase.update!(main_link_text: "Phase link!", main_link_url: "https://consuldemocracy.org")
     render_inline Budgets::PhasesComponent.new(budget)
 
-    expect(page).to have_css(".main-link")
-    expect(page).to have_link("Phase link!", href: "https://consuldemocracy.org")
+    expect(page).to have_link "Phase link!", href: "https://consuldemocracy.org", class: "main-link"
   end
 end