Update articles/components/button/styling.adoc

Co-authored-by: Rolf Smeds <[email protected]>

Author: web-padawan

articles/components/button/styling.adoc

@@ -15,7 +15,7 @@ The following variants can be used to distinguish between actions of different i
 
 [cols="1,3,1"]
 |===
-| Variant | selector | Supported by
+| Variant | CSS selector | Supported by
 
 |Primary
 |`vaadin-button+++<wbr>+++**[theme~="primary"]**`