Fix syntax in Katex markdown file

exampleSite/content.en/docs/shortcodes/katex.md

@@ -9,7 +9,7 @@ KaTeX shortcode let you render math typesetting in markdown document. See [KaTeX
 {{% columns %}}
 
 ```latex
-{{</* katex display=true [class="..."] >}}
+{{</* katex display=true >}}
 f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi
 {{< /katex */>}}
 ```