update formatting for recent lints (dart-lang/browser_launcher#47)

diff --git a/pkgs/browser_launcher/lib/src/chrome.dart b/pkgs/browser_launcher/lib/src/chrome.dart
index 0d52656..7680765 100644
--- a/pkgs/browser_launcher/lib/src/chrome.dart
+++ b/pkgs/browser_launcher/lib/src/chrome.dart
@@ -28,7 +28,7 @@
     final windowsPrefixes = [
       Platform.environment['LOCALAPPDATA'],
       Platform.environment['PROGRAMFILES'],
-      Platform.environment['PROGRAMFILES(X86)']
+      Platform.environment['PROGRAMFILES(X86)'],
     ];
     return p.join(
       windowsPrefixes.firstWhere(