fix typo

Author: navaronbracke

lib/src/mobile_scanner_controller.dart

@@ -104,7 +104,7 @@ class MobileScannerController extends ValueNotifier<MobileScannerState> {
   /// Get the stream of scanned barcodes.
   ///
   /// If an error occurred during the detection of a barcode,
-  /// an [MobileScannerBarcodeException] error is emitted to the stream.
+  /// a [MobileScannerBarcodeException] error is emitted to the stream.
   Stream<BarcodeCapture> get barcodes => _barcodesController.stream;
 
   StreamSubscription<BarcodeCapture?>? _barcodesSubscription;