Remove somewhat incorrect comment.

While no longer used by the helm code, this field is part of the API exposed to helm charts as part of the .Capabilities struct.

Signed-off-by: Marcin Owsiany <marcin@redhat.com>

pkg/chartutil/capabilities.go

@@ -54,7 +54,6 @@ type Capabilities struct {
 	// KubeVersion is the Kubernetes version.
 	KubeVersion KubeVersion
 	// APIVersions are supported Kubernetes API versions.
-	// This field is unused.
 	APIVersions VersionSet
 	// HelmVersion is the build information for this helm version
 	HelmVersion helmversion.BuildInfo