Add missing full stop in docs.

Author: BeMacized

packages/camera/camera_platform_interface/lib/src/platform_interface/camera_platform.dart

@@ -81,15 +81,15 @@ abstract class CameraPlatform extends PlatformInterface {
   /// Starts a video recording
   ///
   /// If no [file] parameter is provided, the recording will be saved to a new file in a temporary location.
-  /// 
+  ///
   /// The file is written on the flight as the video is being recorded.
   /// If a file already exists at the path for the provided file instance, an error will be thrown.
   /// The file can be read as soon as [stopVideoRecording] returns it.
   Future<XFile> startVideoRecording(int cameraId, { XFile file }) {
     throw UnimplementedError('startVideoRecording() is not implemented.');
   }
 
-  /// Stops the video recording and returns the file where it was saved
+  /// Stops the video recording and returns the file where it was saved.
   Future<XFile> stopVideoRecording(int cameraId) {
     throw UnimplementedError('stopVideoRecording() is not implemented.');
   }