pkg/system: remove deprecated IsProcessAlive, IsProcessZombie, KillProcess

These were deprecated in 9d5e754caad0af212545b352e19c3085d8df3281, which
is part of the v24.0.0 release, so we can remove it from master.

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

pkg/process/process_windows.go

@@ -43,10 +43,3 @@ func Kill(pid int) error {
 	}
 	return nil
 }
-
-// Zombie is not supported on Windows.
-//
-// TODO(thaJeztah): remove once we remove the stubs from pkg/system.
-func Zombie(_ int) (bool, error) {
-	return false, nil
-}

pkg/system/process_deprecated.go

@@ -1,27 +0,0 @@
-//go:build linux || freebsd || darwin || windows
-// +build linux freebsd darwin windows
-
-package system
-
-import "github.com/docker/docker/pkg/process"
-
-var (
-	// IsProcessAlive returns true if process with a given pid is running.
-	//
-	// Deprecated: use [process.Alive].
-	IsProcessAlive = process.Alive
-
-	// IsProcessZombie return true if process has a state with "Z"
-	//
-	// Deprecated: use [process.Zombie].
-	//
-	// TODO(thaJeztah): remove the Windows implementation in process once we remove this stub.
-	IsProcessZombie = process.Zombie
-)
-
-// KillProcess force-stops a process.
-//
-// Deprecated: use [process.Kill].
-func KillProcess(pid int) {
-	_ = process.Kill(pid)
-}