Update DAG docs

Author: Krystle Salazar

catalog/DAGs.md

@@ -19,6 +19,7 @@ The following are DAGs grouped by their primary tag:
 1.  [Database](#database)
 1.  [Maintenance](#maintenance)
 1.  [Oauth](#oauth)
+1.  [Other](#other)
 1.  [Provider](#provider)
 1.  [Provider Reingestion](#provider-reingestion)
 
@@ -63,6 +64,12 @@ The following are DAGs grouped by their primary tag:
 | [`oauth2_authorization`](#oauth2_authorization) | `None`            |
 | [`oauth2_token_refresh`](#oauth2_token_refresh) | `0 */12 * * *`    |
 
+## Other
+
+| DAG ID                                                    | Schedule Interval |
+| --------------------------------------------------------- | ----------------- |
+| [`flickr_thumbnails_removal`](#flickr_thumbnails_removal) | `None`            |
+
 ## Provider
 
 | DAG ID                                                          | Schedule Interval | Dated   | Media Type(s) |
@@ -113,6 +120,7 @@ The following is documentation associated with each DAG (where available):
 1.  [`finnish_museums_workflow`](#finnish_museums_workflow)
 1.  [`flickr_audit_sub_provider_workflow`](#flickr_audit_sub_provider_workflow)
 1.  [`flickr_reingestion_workflow`](#flickr_reingestion_workflow)
+1.  [`flickr_thumbnails_removal`](#flickr_thumbnails_removal)
 1.  [`flickr_workflow`](#flickr_workflow)
 1.  [`freesound_workflow`](#freesound_workflow)
 1.  [`image_data_refresh`](#image_data_refresh)
@@ -394,6 +402,11 @@ Output: TSV file containing the images and the respective meta-data.
 
 Notes: https://www.flickr.com/help/terms/api Rate limit: 3600 requests per hour.
 
+## `flickr_thumbnails_removal`
+
+One-time run DAG to remove progressively all the old Flickr thumbnails, as they
+were determined to be unsuitable for the Openverse UI requirements.
+
 ## `flickr_workflow`
 
 Content Provider: Flickr

catalog/dags/flickr_thumbs_removal.py

@@ -1,3 +1,7 @@
+"""
+One-time run DAG to remove progressively all the old Flickr thumbnails,
+as they were determined to be unsuitable for the Openverse UI requirements.
+"""
 import logging
 from datetime import timedelta
 from textwrap import dedent