Fix nullability in docs (flutter#3876)

Update code in docs snippets.

Author: justinmc

packages/url_launcher/url_launcher/CHANGELOG.md

@@ -1,5 +1,6 @@
-## NEXT
+## 6.1.11
 
+* Fixes some url_launcher docs that were missing the null operator (?).
 * Updates minimum Flutter version to 3.3.
 * Aligns Dart and Flutter SDK constraints.
 

packages/url_launcher/url_launcher/lib/src/link.dart

@@ -25,7 +25,7 @@ Future<ByteData> Function(Object?, String) pushRouteToFrameworkFunction =
 /// ```dart
 /// Link(
 ///   uri: Uri.parse('https://flutter.dev'),
-///   builder: (BuildContext context, FollowLink followLink) => ElevatedButton(
+///   builder: (BuildContext context, FollowLink? followLink) => ElevatedButton(
 ///     onPressed: followLink,
 ///     // ... other properties here ...
 ///   )},
@@ -37,7 +37,7 @@ Future<ByteData> Function(Object?, String) pushRouteToFrameworkFunction =
 /// ```dart
 /// Link(
 ///   uri: Uri.parse('/home'),
-///   builder: (BuildContext context, FollowLink followLink) => ElevatedButton(
+///   builder: (BuildContext context, FollowLink? followLink) => ElevatedButton(
 ///     onPressed: followLink,
 ///     // ... other properties here ...
 ///   )},

packages/url_launcher/url_launcher/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for launching a URL. Supports
   web, phone, SMS, and email schemes.
 repository: https://github.com/flutter/packages/tree/main/packages/url_launcher/url_launcher
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+url_launcher%22
-version: 6.1.10
+version: 6.1.11
 
 environment:
   sdk: ">=2.18.0 <4.0.0"