RAG notebook changes on OpenAI API costs and models

[arun-rfai]

Changes

• added comment cells to gsm8k and scifact notebooks on openai api costs
• downsampled data further in both notebooks to reduce cotsts
• now api costs are $3 and $5 only
• reasoning effort knob adjusted in gsm8k, reducing to 6 configs

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this change manually
• I have tested this change in the following environments:
  • Local development
  • Docker environment
  • Other: _______________

[chethan-rfai]

LGTM
This PR is expected to fix: #103