Cleanup activationHookSubscriptions when deactivating package

Released under CC0.

src/package.coffee

@@ -388,6 +388,7 @@ class Package
     @activationPromise = null
     @resolveActivationPromise = null
     @activationCommandSubscriptions?.dispose()
+    @activationHookSubscriptions?.dispose()
     @configSchemaRegisteredOnActivate = false
     @deactivateResources()
     @deactivateKeymaps()