Remove rake task to republish all tags
Remove rake task to republish all tags

We introduced this task to migrate the tags to the publishing-api.
However, the rake task in panopticon
(https://github.com/alphagov/panopticon/blob/ae5426fcebe457ad7d6fa6f9eb7
4666c1762ab94/lib/tasks/migrate_taggings.rake) is actually more suited
for this task because it also sends the `organisation` taggings.

alphagov/publisher,alphagov/publisher,alphagov/publisher