[tool] Fix typo in `publish-plugin` readme (#5107)

script/tool/CHANGELOG.md

diff --git a/script/tool/CHANGELOG.md b/script/tool/CHANGELOG.md
index 214eb68..45f7f52 100644
--- a/script/tool/CHANGELOG.md
+++ b/script/tool/CHANGELOG.md
@@ -1,3 +1,7 @@
+## NEXT
+
+- Updates `publish-plugin` command documentation.
+
 ## 0.8.2
 
 - Adds a new `custom-test` command.

script/tool/README.md

diff --git a/script/tool/README.md b/script/tool/README.md
index 265d386..05be917 100644
--- a/script/tool/README.md
+++ b/script/tool/README.md
@@ -109,11 +109,18 @@
 
 ### Publish a Release
 
-``sh
+**Releases are automated for `flutter/plugins` and `flutter/packages`.**
+
+The manual procedure described here is _deprecated_, and should only be used when
+the automated process fails. Please, read
+[Releasing a Plugin or Package](https://github.com/flutter/flutter/wiki/Releasing-a-Plugin-or-Package)
+on the Flutter Wiki first.
+
+```sh
 cd <path_to_plugins>
 git checkout <commit_hash_to_publish>
-dart run ./script/tool/bin/flutter_plugin_tools.dart publish-plugin --package <package>
-``
+dart run ./script/tool/bin/flutter_plugin_tools.dart publish-plugin --packages <package>
+```
 
 By default the tool tries to push tags to the `upstream` remote, but some
 additional settings can be configured. Run `dart run ./script/tool/bin/flutter_plugin_tools.dart
@@ -127,10 +134,6 @@
 directory and refuse to publish if there are any mismatched files with version
 control present.
 
-Automated publishing is under development. Follow
-[flutter/flutter#27258](https://github.com/flutter/flutter/issues/27258)
-for updates.
-
 ## Updating the Tool
 
 For flutter/plugins, just changing the source here is all that's needed.