[Box] Clean up prop descriptions

Author: laurkim

polaris-react/src/components/Box/Box.tsx

@@ -155,21 +155,21 @@ export interface BoxProps {
   /** Width of container */
   width?: string;
   // These could be moved to new layout component(s) in the future
-  /** Position of the box */
+  /** Position of box */
   position?: Position;
-  /** Top position of the box */
+  /** Top position of box */
   top?: Spacing;
-  /** Bottom position of the box */
+  /** Bottom position of box */
   right?: Spacing;
-  /** Left position of the box */
+  /** Left position of box */
   bottom?: Spacing;
-  /** Right position of the box */
+  /** Right position of box */
   left?: Spacing;
-  /** Opcity of the box */
+  /** Opacity of box */
   opacity?: string;
   /** Visually hide the contents (still announced by screenreader) */
   visuallyHidden?: boolean;
-  /** z-index of the box */
+  /** z-index of box */
   zIndex?: string;
 }