fix: More heading levels so RNs resolve links

[mikemckiernan]

Description

We need to increase the number of heading levels that are possible targets so that the RNs can link to the headings.

This fixes a goof in the RNs where the "Added the rails.output.apply_to_reasoning_traces field" bullet did not end with a link at all.

Related Issue(s)

Checklist

• I've read the CONTRIBUTING guidelines.
• I've updated the documentation if applicable.
• I've added tests if applicable.
• @mentions of the person or team responsible for reviewing proposed changes.

[github-actions]

Documentation preview

https://nvidia.github.io/NeMo-Guardrails/review/pr-1228

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.65%. Comparing base (5a4733f) to head (0176574).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1228   +/-   ##
========================================
  Coverage    68.65%   68.65%           
========================================
  Files          161      161           
  Lines        15978    15978           
========================================
  Hits         10969    10969           
  Misses        5009     5009           

Flag	Coverage Δ
python	68.65% <ø> (ø)

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