refactor: don't use html inside ruby in locations index page

app/views/locations/index.html.erb

@@ -97,7 +97,9 @@
           <% row.cell(text: location.id) %>
           <% row.cell(text: simple_format(location_cell_postcode(location, scheme_location_path(@scheme, location)), { class: "govuk-!-font-weight-bold" }, wrapper_tag: "div")) %>
           <% row.cell(text: location.units) %>
-          <% row.cell(text: simple_format("<span>#{location.type_of_unit}</span>")) %>
+          <% row.cell do %>
+            <span><%= simple_format(location.type_of_unit) %></span>
+          <% end %>
           <% row.cell(text: location.mobility_type) %>
           <% row.cell(text: simple_format(location_cell_location_admin_district(location, "#{scheme_location_path(@scheme, location)}/edit-local-authority"), wrapper_tag: "div")) %>
           <% row.cell(text: location.startdate&.to_formatted_s(:govuk_date)) %>