fix: return items in _get_render_metadata without validate prereq_met

[jignaciopm]

Description

This PR finds a solution to the problem reported in openedx/frontend-app-learning#1546
The endpoint {{domain}}/api/courseware/sequence/{{sequenceId}} was not returning the units (items) when the section (sequence) had a prerequisite.

Before:
391659904-65c09750-21c9-47d2-b4db-ad37ee1c0ac3.webm

After:
https://github.com/user-attachments/assets/c0864e2d-2ab0-4aa0-bbac-c94f31c35ba5

Supporting information

openedx/frontend-app-learning#1546

Testing instructions

1. Configuring a subsection as a prerequisite
2. Making that subsection the prerequisite of another subsection
3. Go to the prerequisite subsection and navigate to the gated subsection
4. If I try to go to the previous unit right before the gated subsection, the sequence buttons works
5. If from the sidebar I try entering one of the units in the gated subsection, and the previous button works