fix(Modal): remove non-existent prop (#4463)

Author: Rexogamer

website/versioned_docs/version-0.76/modal.md

@@ -126,16 +126,6 @@ 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`.
-
-| Type            | Default |
-| --------------- | ------- |
-| [color](colors) | white   |
-
----
-
 ### `hardwareAccelerated` <div class="label android">Android</div>
 
 The `hardwareAccelerated` prop controls whether to force hardware acceleration for the underlying window.