When desktop support is not present in an existing project, certain
flutter tool commands raise an error that direct the user to
documentation on how to add desktop support to an existing Flutter
project. In a recent revamp of the webside, the URL was very slightly
changed (flutter.dev -> docs.flutter.dev).

This updates the error message to output the new URL.

Issue: https://github.com/flutter/flutter/issues/94398

* f5ebc91a3 Roll Fuchsia Linux SDK from DS-3oCidC... to 3-zk7OPWY... (flutter/engine#30792)

* 1064abe4c Roll Skia from 7a14f783bda3 to 41e994f735d9 (2 revisions) (flutter/engine#30793)

* a4a505b96 Revert "Roll Fuchsia Linux SDK from DS-3oCidC... to 3-zk7OPWY... (#30792)" (flutter/engine#30798)

* 6389ee3e0 [fuchsia] Bump buildroot/ to fix Fuchsia SDK roll (flutter/engine#30794)

* f94c8e0ee Implemented library uri support for FlutterFragmentActivities (flutter/engine#30790)

* c18074871 Roll Fuchsia Mac SDK from 9rr72kcgt... to LxyiyZWks... (flutter/engine#30796)

* 6927c00de Roll Dart SDK from 3061b1d4c117 to 099f7f57767c (5 revisions) (flutter/engine#30797)

* d889c0cda Roll Skia from 41e994f735d9 to 345587df72ae (3 revisions) (flutter/engine#30800)

* d53514e7e Remove unused setPersistentIsolateData function (flutter/engine#30795)

* f1b45482a Variable Refresh Rate Display (flutter/engine#30223)

* 0139f6e28 Roll Skia from 345587df72ae to 30fdea3d8fd5 (2 revisions) (flutter/engine#30802)

* 643b2787f Add 'keyCode' field to eventData map created from html keyboard events. (flutter/engine#30801)

* c9b0f70b0 Roll Dart SDK from f59531cc2973 to a6b70ecf9e48 (5 revisions) (flutter/engine#30776)

* b5a9cfd53 Roll Skia from 55b4dc3f7a1c to 8a85ab0d96a1 (1 revision) (flutter/engine#30777)

* 58305d13a Roll Skia from dd575bc0f1f5 to 0056f3f006de (2 revisions) (flutter/engine#30765)

* 92a4f99c0 Allow additional expose_dirs in flutter_runner (flutter/engine#30749)

* 358605ca0 [web] Remove EngineParagraph and ParagraphGeometricStyle (flutter/engine#30766)

* 8b9f625bd Remove glitch when displaying platform views (flutter/engine#30724)

* bd6533032 Add missing dependencies to the background image app (flutter/engine#30769)

* 65dfc9e3b [android] Remove the FlutterView casting, add a @NonNull and fix code style (flutter/engine#30734)

* 00e2a47e0 Roll Skia from 0056f3f006de to 3e1354a592bc (3 revisions) (flutter/engine#30771)

* 279e3af0a Implemented library uri support for FlutterFragments and FlutterActivities (flutter/engine#30726)

* 36ad9f1bb Roll Skia from 3e1354a592bc to 55b4dc3f7a1c (1 revision) (flutter/engine#30773)

Clarify in the docs about what an invalid selection means, contrasted with a 0,0 selection.