refactor: throw an error when removing a non-existing plugin

Related to #2

src/routes/plugin-register-route.ts

@@ -14,6 +14,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 import {
+  SCNotFoundErrorResponse,
   SCPluginAlreadyRegisteredErrorResponse,
   SCPluginMetaData,
   SCPluginRegisterRequest,
@@ -85,11 +86,9 @@ function addPlugin(plugin: SCPluginMetaData): SCPluginRegisterResponse {
  */
 function removePlugin(route: string): SCPluginRegisterResponse {
   if (!plugins.has(route)) {
-    // TODO: throw error when plugin that is to be removed is not already registered (after @openstapps/core update)
-    // throw new SCNotFoundErrorResponse(
-    //   isTestEnvironment,
-    // );
-    return {success: false};
+    throw new SCNotFoundErrorResponse(
+      isTestEnvironment,
+    );
   }
   // remove the plugin information using its route as a key
   plugins.delete(route);