Remove import instance from list using Migrate Tools module

I'm trying to remove an rss reference of a migration. Once I put the yaml code into the Migrate module in the drupal admin interface, it creates a reference to that yaml code, but there is no one in the UI that I can see the reference. The Migrate Tools module gives me access to drush commands, but none of which could remove a reference.

Does anyone know how to delete a reference to an import? I can see references through the command line using $ drush ms

I searched but could only find using this, but it doesn't work.

$ drush php

>>> Drupal::configFactory()->getEditable('migrate_plus.migration.my_rss_importer')->delete();

Here is the list of imports from the CLI I am trying to remove. Just for reference "migrate_plus" mentioned in the code above is another module that compliments the migrate module.

Group: Default (default)      Status  Total  Imported  Unprocessed  Last imported
 berkeley_news_rss_importer_1  Idle    20     20        0            2017-12-09 23:08:36
 berkeley_news_rss_importer_2  Idle    20     20        0            2017-12-09 23:12:34
 berkeley_news_rss_importer_3  Idle    20     20        0            2017-12-09 23:14:03
 berkeley_news_rss_importer_4  Idle    20     20        0            2017-12-09 23:20:04
 berkeley_news_rss_importer_5  Idle    20     20        0            2017-12-09 23:33:17
 berkeley_news_rss_importer_6  Idle    20     20        0            2017-12-09 23:42:26
 berkeley_news_rss_importer_7  Idle    20     0         0            2017-12-10 00:11:17
 berkeley_news_rss_importer_8  Idle    20     20        0            2017-12-11 09:46:45
 berkeley_news_rss_importer_9  Idle    20     0         20