[system][docs] Update typo on the sx prop page (@bricker) (#42078)

Co-authored-by: Danilo Leal <[email protected]>

docs/data/system/getting-started/the-sx-prop/the-sx-prop.md

@@ -1,6 +1,6 @@
 # The sx prop
 
-<p class="description">The sx prop is a shortcut for defining custom styles that has access to the theme.</p>
+<p class="description">The sx prop is a shortcut for defining custom styles that have access to the theme.</p>
 
 The `sx` prop lets you work with a superset of CSS that packages all of the style functions exposed in `@mui/system`.
 You can specify any valid CSS using this prop, as well as many _theme-aware_ properties that are unique to MUI System.