[google_sign_in, url_launcher] Document unendorsement of web.

Add some documentation to the CHANGELOG to mention that the plugin
doesn't support web in the current prerelease state.

Author: ditman

packages/google_sign_in/google_sign_in/CHANGELOG.md

@@ -1,6 +1,11 @@
+## 5.0.0-nullsafety.1
+
+* Document that the web plugin is not endorsed in the `nullsafety` prerelease for now.
+
 ## 5.0.0-nullsafety
 
 * Migrate to nnbd.
+* **Breaking change**: web plugins aren't endorsed in null-safe plugins yet.
 
 ## 4.5.9
 

packages/google_sign_in/google_sign_in/pubspec.yaml

@@ -2,7 +2,7 @@ name: google_sign_in
 description: Flutter plugin for Google Sign-In, a secure authentication system
   for signing in with a Google account on Android and iOS.
 homepage: https://github.com/flutter/plugins/tree/master/packages/google_sign_in/google_sign_in
-version: 5.0.0-nullsafety
+version: 5.0.0-nullsafety.1
 
 flutter:
   plugin:
@@ -12,8 +12,8 @@ flutter:
         pluginClass: GoogleSignInPlugin
       ios:
         pluginClass: FLTGoogleSignInPlugin
-      web:
-        default_package: google_sign_in_web
+      #web:
+      #  default_package: google_sign_in_web
 
 dependencies:
   google_sign_in_platform_interface: ^2.0.0-nullsafety

packages/url_launcher/url_launcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.0.0-nullsafety.5
+
+* Document that the web plugin is not endorsed in the `nullsafety` prerelease for now.
+
 ## 6.0.0-nullsafety.4
 
 * Update the example app: remove the deprecated `RaisedButton` and `FlatButton` widgets.
@@ -17,6 +21,7 @@
 ## 6.0.0-nullsafety
 
 * Migrate to null safety.
+* **Breaking change**: web plugins aren't endorsed in null-safe plugins yet.
 
 ## 5.7.13
 

packages/url_launcher/url_launcher/pubspec.yaml

@@ -2,7 +2,7 @@ name: url_launcher
 description: Flutter plugin for launching a URL on Android and iOS. 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.4
+version: 6.0.0-nullsafety.5
 
 flutter:
   plugin: