cli-plugins/manager: remove legacy system-wide cli-plugin path

commit 4d3a76d71e updated the list of directories
for discovering CLI plugins, adding `%ProgramFiles%\Docker\cli-plugins` for
system-wide plugins.

For backward compatibility, the `%PROGRAMDATA%\Docker\cli-plugins` was kept,
however, this location is no longer used, and not generally recommended for
storing non-data content (such as CLI plugin binaries). From the [ProgramData]
documentation:

> ProgramData specifies the path to the program-data folder (normally C:\ProgramData).
> Unlike the Program Files folder, this folder can be used by applications to store
> data for standard users, because it does not require elevated permissions.

It also mentions "It can’t contain any serviceable components.", effectively
meaning that these paths should not contain data that is managed (through
updates etc.), making it a poor choice for installing "system wide" CLI plugins.

This patch removes the path from the list, given that this location is no longer
used by Docker Desktop, and the CLI-plugin API is considered an internal
implementation (since 459c6082f8).

[ProgramData]: https://learn.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/microsoft-windows-shell-setup-folderlocations-programdata

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli-plugins/manager/manager_windows.go

@@ -16,6 +16,5 @@ import (
 //
 // [ConfigFile.CLIPluginsExtraDirs]: https://pkg.go.dev/github.com/docker/cli@v26.1.4+incompatible/cli/config/configfile#ConfigFile.CLIPluginsExtraDirs
 var defaultSystemPluginDirs = []string{
-	filepath.Join(os.Getenv("ProgramData"), "Docker", "cli-plugins"),
 	filepath.Join(os.Getenv("ProgramFiles"), "Docker", "cli-plugins"),
 }