fix(qa): read properly var to fix streaming

[krokoko]

Fixes #

• Fix issue where streaming is not working properly: variable for streaming was not read correctly
• test with both streaming enabled and disable for several models
• update documentation to include that streaming is supported for qa

Example:
Test streaming enabled with claude 3 - rag approach. Callback on new llm token correctly called and response generated

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.13%. Comparing base (b4584f0) to head (f3cf4af).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #341      +/-   ##
==========================================
- Coverage   96.35%   96.13%   -0.22%     
==========================================
  Files          40       40              
  Lines        9682     9682              
  Branches      279      277       -2     
==========================================
- Hits         9329     9308      -21     
- Misses        353      374      +21     

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