move period to fix lint check (facebook#4282)

Author: alanleedev

docs/modal.md

@@ -128,7 +128,7 @@ Possible values:
 
 ### `backdropColor`
 
-The `backdropColor` of the modal (or background color of the modal's container). Defaults to `white` if not provided and transparent is `false`. Ignored if `transparent` is `true`.
+The `backdropColor` of the modal (or background color of the modal's container.) Defaults to `white` if not provided and transparent is `false`. Ignored if `transparent` is `true`.
 
 | Type            | Default |
 | --------------- | ------- |