Chore: Remove dead code (#28664)

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/plugins/backendplugin/grpcplugin/client.go

@@ -66,11 +66,6 @@ type PluginDescriptor struct {
 	startFns         PluginStartFuncs
 }
 
-// PluginID returns the plugin ID.
-func (pd PluginDescriptor) PluginID() string {
-	return pd.pluginID
-}
-
 // getV2PluginSet returns list of plugins supported on v2.
 func getV2PluginSet() goplugin.PluginSet {
 	return goplugin.PluginSet{