release: Finish preparation for 4.21.0

.release.cfg

@@ -1,31 +1,34 b''
 [DEFAULT]
 done = false
 
 [task:bump_version]
 done = true
 
 [task:rc_tools_pinned]
 done = true
 
 [task:fixes_on_stable]
+done = true
 
 [task:pip2nix_generated]
+done = true
 
 [task:changelog_updated]
+done = true
 
 [task:generate_api_docs]
 done = true
 
 [task:updated_translation]
 done = true
 
 [release]
-state = in_progress
+state = prepared
 version = 4.21.0
 
 [task:generate_js_routes]
 
 [task:updated_trial_license]
 
 [task:generate_oss_licenses]