[url_launcher] Re-endorse web implementation. (flutter#3557)

This change re-endorses url_launcher_web, now that it's been migrated to null-safety.

Author: ditman

packages/url_launcher/url_launcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.0.0-nullsafety.7
+
+* Re-endorse `url_launcher_web` in the `nullsafety` prerelease.
+
 ## 6.0.0-nullsafety.6
 
 * Correct statement in description about which platforms url_launcher supports.

packages/url_launcher/url_launcher/pubspec.yaml

@@ -2,7 +2,7 @@ name: url_launcher
 description: Flutter plugin for launching a URL. Supports
   web, phone, SMS, and email schemes.
 homepage: https://github.com/flutter/plugins/tree/master/packages/url_launcher/url_launcher
-version: 6.0.0-nullsafety.6
+version: 6.0.0-nullsafety.7
 
 flutter:
   plugin:
@@ -12,9 +12,8 @@ flutter:
         pluginClass: UrlLauncherPlugin
       ios:
         pluginClass: FLTURLLauncherPlugin
-      # TODO(mvanbeusekom): Temporary disabled until web is migrated to nnbd (advised by @blasten).
-      #web:
-      #  default_package: url_launcher_web
+      web:
+        default_package: url_launcher_web
       linux:
         default_package: url_laucher_linux
       macos:
@@ -34,8 +33,7 @@ dependencies:
   url_launcher_linux: ^0.1.0-nullsafety
   url_launcher_macos: ^0.1.0-nullsafety
   url_launcher_windows: ^0.1.0-nullsafety
-  # TODO(mvanbeusekom): Temporary disabled until web is migrated to nnbd (advised by @blasten).
-  #url_launcher_web: ^0.1.3
+  url_launcher_web: ^2.0.0-nullsafety
 
 dev_dependencies:
   flutter_test: