Remove support for plugin format v1

Summary:
Do not list plugins packaged with format v1 in Plugin Manager.

Changelog: removed support for plugins packaged using legacy format (v1), so they won't appear in Plugin Manager anymore.

Reviewed By: passy

Differential Revision: D23681402

fbshipit-source-id: 1c9496ba6b739069d67228a0f4250f2f01aabd4d

desktop/plugin-lib/src/getUpdatablePlugins.ts

@@ -91,6 +91,9 @@ export async function getUpdatablePlugins(): Promise<UpdatablePluginDetails[]> {
           getPluginInstallationDir(notInstalledPlugin.name),
           pkg,
         );
+        if (npmPluginDetails.specVersion === 1) {
+          return null;
+        }
         return {
           ...npmPluginDetails,
           updateStatus: {