Force legacy TOC to render at lower resolutions

- If TOC A/B test is enabled, page is in treatment group, and
viewport is below tablet, force legacy TOC to render.
- If TOC A/B test is disabled and new TOC feature is enabled,
and viewport is below tablet, neither TOC should render.

Bug: T300975
Change-Id: Ib30c3473eb47d6ac60924f40ccd0e42d29625407

resources/skins.vector.styles/components/TableOfContents.less

@@ -134,3 +134,11 @@
 		display: block;
 	}
 }
+
+// T300975 following media query for TOC experiment treatment
+// class can be removed once associated A/B test is over.
+@media ( max-width: @width-breakpoint-tablet ) {
+	.skin-vector-toc-experiment-treatment #toc {
+		display: table;
+	}
+}