Remove blocked_by code

What does this MR do?

This is last MR removing blocked_by related code. after removal blocked_by while keeping only blocks we simplified queries.

This MR removes the remains in the code.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Related to: #281703 (closed)