fix css specificity issue (#135245)

src/plugins/vis_types/timeseries/public/application/components/vis_types/markdown/vis.js

@@ -58,7 +58,15 @@ function MarkdownVisualization(props) {
         {markdownError && <ErrorComponent error={markdownError} />}
         <ClassNames>
           {({ css, cx }) => (
-            <div className={cx(contentClasses, css(model.markdown_css))}>
+            <div
+              className={cx(
+                contentClasses,
+                // wrapping select for markdown body to make sure selector specificity wins over base styles
+                css(`.kbnMarkdown__body {
+                  ${model.markdown_css}
+                }`)
+              )}
+            >
               <div>
                 {!markdownError && (
                   <Markdown