Remove docs redirects raketask

What does this MR do?

In !62131 (merged), we added a raketask that was trying to automate the redirects cleanup.

Since we needed to have this implemented in all upstream projects (GitLab, Omnibus, Charts, Runner), and to avoid duplication, we migrated this task to the gitlab-docs project gitlab-docs!1845 (merged).

Thus, we don't need the task anymore.

Related: technical-writing#439 (closed)

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• [-] I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.