docs: fix output rail doc

[andompesta]

Description

Fix some issues on output streaming rails documentation.
Specifically the streaming.enabled field was missing

Related Issue(s)

I haven't opened a proper issue for that

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.

[mikemckiernan]

Thanks very much for the contribution and corrections! If you don't have time for the requested changes, just let me know and I can add them to this PR and bring them in with your changes.

[github-actions]

Documentation preview

https://nvidia.github.io/NeMo-Guardrails/review/pr-1159

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #1159   +/-   ##
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  Coverage           ?   68.24%           
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  Files              ?      161           
  Lines              ?    15938           
  Branches           ?        0           
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  Hits               ?    10877           
  Misses             ?     5061           
  Partials           ?        0           

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