Ignore rules for media-feature-range syntax

We cannot fix the Stylint error by using the new CSS media query range syntax,
as we will get a new error when trying to compile our CSS. The reason for this is
that we use the sassc-rails gem to compile our CSS, this includes the deprecated
LibSass library which does not understand the new CSS media query range syntax.

app/assets/stylesheets/views/_covid.scss

@@ -7,7 +7,7 @@ $c19-landing-page-header-background: govuk-colour("blue");
 .covid__page {
   .govuk-grid-column-one-third,
   .govuk-grid-column-two-thirds {
-    @media (max-width: 950px) {
+    @media (max-width: 950px) { // stylelint-disable-line media-feature-range-notation
       width: 100%;
     }
   }