specs-go: add missing deprecation comment for Hooks.Prestart

Hooks.Prestart was deprecated in c166268
(v1.0.2), but the field did not have a correctly formatted deprecation comment.

This patch updates the field's GoDoc to have a correctly formatted deprecation
comment, which will allow linters and IDEs to detect the deprecation status
of this feature.

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

specs-go/config.go

@@ -187,6 +187,10 @@ type Hook struct {
 type Hooks struct {
 	// Prestart is Deprecated. Prestart is a list of hooks to be run before the container process is executed.
 	// It is called in the Runtime Namespace
+	//
+	// Deprecated: use [Hooks.CreateRuntime], [Hooks.CreateContainer], and
+	// [Hooks.StartContainer] instead, which allow more granular hook control
+	// during the create and start phase.
 	Prestart []Hook `json:"prestart,omitempty"`
 	// CreateRuntime is a list of hooks to be run after the container has been created but before pivot_root or any equivalent operation has been called
 	// It is called in the Runtime Namespace