Deprecate and remove hierarchy information from linkable-elements.json

[d-ronnqvist]

Bug/issue #, if applicable:

Summary

This deprecates and removes hierarchy information from the "linkable-elements.json" file.

This information isn't useful for the purpose of linking to these elements and isn't used anywhere when these elements are linked to.
It could be argued that this information provides a way for tools to read reconstruct the documentation hierarchy. However;

• it is too limited to accurately represent the documentation hierarchy.
• this file isn't meant to represent the documentation hierarchy. Clients who need this information should either, read the index/index.json file or pass --enable-experimental-external-link-support and use the information in "link-hierarchy.json" file instead.

Dependencies

None

Testing

Pass the --emit-digest flag to DocC. The created "linkable-elements.json" file shouldn't contain any "taskGroups" information anymore.

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added Updated tests
• Ran the ./bin/test script and it succeeded
• [ ] Updated documentation if necessary